Method and apparatus for tranceiving common control message in wireless access system supporting narrow band internet of things

ABSTRACT

Provided are methods for repeatedly transceiving a common control message for a machine-type communication (MTC) terminal in a wireless access system supporting MTC, and apparatuses supporting the methods. A method for receiving a common control message for an MTC terminal in a wireless access system supporting MTC according to one embodiment of the present invention may comprise the steps of: receiving a channel status information reference signal (CSI-RS); and receiving a common control message from a subframe in which the CSI-RS is received. Here, the common control message can be configured so as to be repeatedly transmitted from a previously configured number of subframes comprising the subframe.

TECHNICAL FIELD

The present disclosure relates to a wireless access system supportingNarrow Band Internet of Things (NB-IoT), and more particularly, to amethod and apparatus for transmitting and receiving a common controlmessage and/or data.

BACKGROUND ART

Wireless access systems have been widely deployed to provide varioustypes of communication services such as voice or data. In general, awireless access system is a multiple access system that supportscommunication of multiple users by sharing available system resources (abandwidth, transmission power, etc.) among them. For example, multipleaccess systems include a Code Division Multiple Access (CDMA) system, aFrequency Division Multiple Access (FDMA) system, a Time DivisionMultiple Access (TDMA) system, an Orthogonal Frequency Division MultipleAccess (OFDMA) system, and a Single Carrier Frequency Division MultipleAccess (SC-FDMA) system.

DISCLOSURE Technical Problem

An aspect of the present disclosure is to provide a method fortransmitting and receiving data and/or control information for a NarrowBand Internet of Things (NB-IoT) User Equipment (UE).

Another aspect of the present disclosure is to provide a method forrepeatedly transmitting and receiving a common control message for anNB-IoT UE.

Another aspect of the present disclosure is to provide a method forallocating a bandwidth for transmitting control information and/data toan NB-IoT UE.

Another aspect of the present disclosure is to provide apparatusessupporting these methods.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

The present disclosure provides a method and apparatuses fortransmitting and receiving a common control message and/or data in awireless access system supporting Narrow Band Internet of Things(NB-IoT).

In an aspect of the present disclosure, a method for transmitting acommon control message in a wireless access system supporting NB-IoTincludes allocating a bandwidth for the NB-IoT, and transmitting acommon control message in the allocated bandwidth. The bandwidth may beconfigured to be aligned with a boundary of a Physical Resource Block(PRB) used in a legacy system, and a PRB minimizing an offset between acenter frequency of the bandwidth and a center frequency of the PRB maybe allocated as the bandwidth for the NB-IoT, in consideration of abandwidth of the legacy system.

In another aspect of the present disclosure, an apparatus fortransmitting a common control message in a wireless access systemsupporting NB-IoT includes a transmitter, and a processor for supportingtransmission of a common control message. The processor may beconfigured to allocate a bandwidth for the NB-IoT, and transmit thecommon control message in the allocated bandwidth by controlling thetransmitter. The bandwidth may be configured to be aligned with aboundary of a PRB used in a legacy system, and a PRB minimizing anoffset between a center frequency of the bandwidth and a centerfrequency of the PRB may be allocated as the bandwidth for the NB-IoT,in consideration of a bandwidth of the legacy system.

Virtual Resource Blocks (VRBs) mapped to the PRB allocated as thebandwidth for the NB-IoT may be used for the transmission of the commoncontrol message.

The bandwidth may be allocated, with a VRB affecting center 6 RBs of thelegacy system avoided.

The common control message may be transmitted repeatedly a predeterminednumber of times.

It is preferred that the PRB allocated as the bandwidth for the NB-IoTis not used as a Distributed Virtual Resource Block (DVRB) in the legacysystem.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

Advantageous Effects

As is apparent from the above description, the embodiments of thepresent disclosure have the following effects.

First, data and/or control information for a Narrow Band Internet ofThings (NB-IoT) User Equipment (UE) may be transmitted and receivedefficiently.

Secondly, it may be configured that if an NB-IoT system operates in anin-band mode, the effect of the in-band-mode operation on a legacysystem is minimized.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain the principle of thedisclosure. In the drawings:

FIG. 1 is a view illustrating physical channels and a signaltransmission method using the physical channels;

FIG. 2 is a view illustrating exemplary radio frame structures;

FIG. 3 is a view illustrating an exemplary resource grid for theduration of a downlink slot;

FIG. 4 is a view illustrating an exemplary structure of an uplinksubframe;

FIG. 5 is a view illustrating an exemplary structure of a downlinksubframe;

FIG. 6 is a view illustrating an example of Component Carriers (CCs) andCarrier Aggregation (CA) in a Long Term Evolution-Advanced (LTE-A)system;

FIG. 7 is a view illustrating a subframe structure based oncross-carrier scheduling in the LTE-A system;

FIG. 8 is a conceptual view of a Coordinated Multi-Point (CoMP) systemoperating in a CA environment;

FIG. 9 is a view illustrating an exemplary subframe to whichCell-specific Reference Signals (CRSs) are allocated, which may be usedin embodiments of the present disclosure;

FIG. 10 is a view illustrating exemplary subframes to which ChannelState Information Reference Signals (CSI-RSs) are allocated according tonumbers of antenna ports, which may be used in embodiments of thepresent disclosure;

FIG. 11 is a view illustrating exemplary multiplexing of a legacyPhysical Downlink Control Channel (PDCCH), a Physical Downlink SharedChannel (PDSCH), and an Enhanced PDCCH (EPDCCH) in an LTE/LTE-A system;

FIG. 12 is a view illustrating a method for repeatedly transmitting aPDCCH, and a method for setting Redundancy Versions (RVs);

FIG. 13 is a view illustrating a method for transmitting CSI-RSs in thecase of repeated transmissions of a Machine Type Communication (MTC)System Information Block (SIB);

FIG. 14 is a view illustrating a relationship between the centerfrequency of an NB-IoT in an in-band mode and the center frequency of anLTE/LTE-A system;

FIG. 15 is a view illustrating a method for allocating a bandwidth fortransmitting a common control signal or data to an NB-IoT User Equipment(UE); and

FIG. 16 is a block diagram of apparatuses for performing the methodsdescribed in FIGS. 1 to 13.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present disclosure as described below in detailprovide a method and apparatuses for using a heterogeneous networksignal to measure the location of a User Equipment (UE).

The embodiments of the present disclosure described below arecombinations of elements and features of the present disclosure inspecific forms. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present disclosure may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present disclosure may be rearranged. Someconstructions or elements of any one embodiment may be included inanother embodiment and may be replaced with corresponding constructionsor features of another embodiment.

In the description of the attached drawings, a detailed description ofknown procedures or steps of the present disclosure will be avoided lestit should obscure the subject matter of the present disclosure. Inaddition, procedures or steps that could be understood to those skilledin the art will not be described either.

Throughout the specification, when a certain portion “includes” or“comprises” a certain component, this indicates that other componentsare not excluded and may be further included unless otherwise noted. Theterms “unit”, “-or/er” and “module” described in the specificationindicate a unit for processing at least one function or operation, whichmay be implemented by hardware, software or a combination thereof. Inaddition, the terms “a or an”, “one”, “the” etc. may include a singularrepresentation and a plural representation in the context of the presentdisclosure (more particularly, in the context of the following claims)unless indicated otherwise in the specification or unless contextclearly indicates otherwise.

In the embodiments of the present disclosure, a description is mainlymade of a data transmission and reception relationship between a BaseStation (BS) and a User Equipment (UE). A BS refers to a terminal nodeof a network, which directly communicates with a UE. A specificoperation described as being performed by the BS may be performed by anupper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with a fixed station, aNode B, an evolved Node B (eNode B or eNB), an Advanced Base Station(ABS), an access point, etc.

In the embodiments of the present disclosure, the term terminal may bereplaced with a UE, a Mobile Station (MS), a Subscriber Station (SS), aMobile Subscriber Station (MSS), a mobile terminal, an Advanced MobileStation (AMS), etc.

A transmission end is a fixed and/or mobile node that provides a dataservice or a voice service and a reception end is a fixed and/or mobilenode that receives a data service or a voice service. Therefore, a UEmay serve as a transmission end and a BS may serve as a reception end,on an UpLink (UL). Likewise, the UE may serve as a reception end and theBS may serve as a transmission end, on a DownLink (DL).

The embodiments of the present disclosure may be supported by standardspecifications disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802.xx system, a 3rd Generation Partnership Project (3GPP) system, a3GPP Long Term Evolution (LTE) system, and a 3GPP2 system. Inparticular, the embodiments of the present disclosure may be supportedby the standard specifications, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS36.213, 3GPP TS 36.321 and 3GPP TS 36.331. That is, the steps or parts,which are not described to clearly reveal the technical idea of thepresent disclosure, in the embodiments of the present disclosure may beexplained by the above standard specifications. All terms used in theembodiments of the present disclosure may be explained by the standardspecifications.

Reference will now be made in detail to the embodiments of the presentdisclosure with reference to the accompanying drawings. The detaileddescription, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present disclosure, rather than to show the only embodiments thatcan be implemented according to the disclosure.

The following detailed description includes specific terms in order toprovide a thorough understanding of the present disclosure. However, itwill be apparent to those skilled in the art that the specific terms maybe replaced with other terms without departing the technical spirit andscope of the present disclosure.

Hereinafter, 3GPP LTE/LTE-A systems are explained, which are examples ofwireless access systems.

The embodiments of the present disclosure can be applied to variouswireless access systems such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), etc.

CDMA may be implemented as a radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented asa radio technology such as Global System for Mobile communications(GSM)/General packet Radio Service (GPRS)/Enhanced Data Rates for GSMEvolution (EDGE). OFDMA may be implemented as a radio technology such asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA(E-UTRA), etc.

UTRA is a part of Universal Mobile Telecommunications System (UMTS).3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMAfor DL and SC-FDMA for UL. LTE-Advanced (LTE-A) is an evolution of 3GPPLTE. While the embodiments of the present disclosure are described inthe context of a 3GPP LTE/LTE-A system in order to clarify the technicalfeatures of the present disclosure, the present disclosure is alsoapplicable to an IEEE 802.16e/m system, etc.

1.3GPP LTE/LTE-A System

In a wireless access system, a UE receives information from an eNB on aDL and transmits information to the eNB on a UL. The informationtransmitted and received between the UE and the eNB includes generaldata information and various types of control information. There aremany physical channels according to the types/usages of informationtransmitted and received between the eNB and the UE.

1.1 System Overview

FIG. 1 illustrates physical channels and a general signal transmissionmethod using the physical channels, which may be used in embodiments ofthe present disclosure.

When a UE is powered on or enters a new cell, the UE performs initialcell search (S11). The initial cell search involves acquisition ofsynchronization to an eNB. Specifically, the UE synchronizes its timingto the eNB and acquires information such as a cell Identifier (ID) byreceiving a Primary Synchronization Channel (P-SCH) and a SecondarySynchronization Channel (S-SCH) from the eNB.

Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the eNB.

During the initial cell search, the UE may monitor a DL channel state byreceiving a Downlink Reference Signal (DL RS).

After the initial cell search, the UE may acquire more detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation of the PDCCH (S12).

To complete connection to the eNB, the UE may perform a random accessprocedure with the eNB (S13 to S16). In the random access procedure, theUE may transmit a preamble on a Physical Random Access Channel (PRACH)(S13) and may receive a PDCCH and a PDSCH associated with the PDCCH(S14). In the case of contention-based random access, the UE mayadditionally perform a contention resolution procedure includingtransmission of an additional PRACH (S15) and reception of a PDCCHsignal and a PDSCH signal corresponding to the PDCCH signal (S16).

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S17) and transmit a Physical Uplink Shared Channel (PUSCH)and/or a Physical Uplink Control Channel (PUCCH) to the eNB (S18), in ageneral UL/DL signal transmission procedure.

Control information that the UE transmits to the eNB is genericallycalled Uplink Control Information (UCI). The UCI includes a HybridAutomatic Repeat and reQuest Acknowledgement/Negative Acknowledgement(HARQ-ACK/NACK), a Scheduling Request (SR), a Channel Quality Indicator(CQI), a Precoding Matrix Index (PMI), a Rank Indicator (RI), etc.

In the LTE system, UCI is generally transmitted on a PUCCH periodically.However, if control information and traffic data should be transmittedsimultaneously, the control information and traffic data may betransmitted on a PUSCH. In addition, the UCI may be transmittedaperiodically on the PUSCH, upon receipt of a request/command from anetwork.

FIG. 2 illustrates exemplary radio frame structures used in embodimentsof the present disclosure.

FIG. 2(a) illustrates frame structure type 1. Frame structure type 1 isapplicable to both a full Frequency Division Duplex (FDD) system and ahalf FDD system.

One radio frame is 10 ms (Tf=307200·Ts) long, including equal-sized 20slots indexed from 0 to 19. Each slot is 0.5 ms (Tslot=15360·Ts) long.One subframe includes two successive slots. An ith subframe includes2ith and (2i+1)th slots. That is, a radio frame includes 10 subframes. Atime required for transmitting one subframe is defined as a TransmissionTime Interval (TTI). Ts is a sampling time given as Ts=1/(15kHz×2048)=3.2552×10−8 (about 33 ns). One slot includes a plurality ofOrthogonal Frequency Division Multiplexing (OFDM) symbols or SC-FDMAsymbols in the time domain by a plurality of Resource Blocks (RBs) inthe frequency domain.

A slot includes a plurality of OFDM symbols in the time domain. SinceOFDMA is adopted for DL in the 3GPP LTE system, one OFDM symbolrepresents one symbol period. An OFDM symbol may be called an SC-FDMAsymbol or symbol period. An RB is a resource allocation unit including aplurality of contiguous subcarriers in one slot.

In a full FDD system, each of 10 subframes may be used simultaneouslyfor DL transmission and UL transmission during a 10-ms duration. The DLtransmission and the UL transmission are distinguished by frequency. Onthe other hand, a UE cannot perform transmission and receptionsimultaneously in a half FDD system.

The above radio frame structure is purely exemplary. Thus, the number ofsubframes in a radio frame, the number of slots in a subframe, and thenumber of OFDM symbols in a slot may be changed.

FIG. 2(b) illustrates frame structure type 2. Frame structure type 2 isapplied to a Time Division Duplex (TDD) system. One radio frame is 10 ms(Tf=307200·Ts) long, including two half-frames each having a length of 5ms (=153600·Ts) long. Each half-frame includes five subframes each being1 ms (=30720·Ts) long. An ith subframe includes 2ith and (2i+1)th slotseach having a length of 0.5 ms (Tslot=15360·Ts). Ts is a sampling timegiven as Ts=1/(15 kHz×2048)=3.2552×10-8 (about 33 ns).

A type-2 frame includes a special subframe having three fields, DownlinkPilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot(UpPTS). The DwPTS is used for initial cell search, synchronization, orchannel estimation at a UE, and the UpPTS is used for channel estimationand UL transmission synchronization with a UE at an eNB. The GP is usedto cancel UL interference between a UL and a DL, caused by themulti-path delay of a DL signal.

[Table 1] below lists special subframe configurations (DwPTS/GP/UpPTSlengths).

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink Special UpPTS UpPTS subframe Normal cyclic Extended cyclicNormal cyclic Extended cyclic configuration DwPTS prefix in uplinkprefix in uplink DwPTS prefix in uplink prefix in uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — —9 13168 · T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL resource grid for theduration of one DL slot, which may be used in embodiments of the presentdisclosure.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot includes 7 OFDM symbols in the time domainand an RB includes 12 subcarriers in the frequency domain, to which thepresent disclosure is not limited.

Each element of the resource grid is referred to as a Resource Element(RE). An RB includes 12×7 REs. The number of RBs in a DL slot, NDLdepends on a DL transmission bandwidth. A UL slot may have the samestructure as a DL slot.

FIG. 4 illustrates a structure of a UL subframe which may be used inembodiments of the present disclosure.

Referring to FIG. 4, a UL subframe may be divided into a control regionand a data region in the frequency domain. A PUCCH carrying UCI isallocated to the control region and a PUSCH carrying user data isallocated to the data region. To maintain a single carrier property, aUE does not transmit a PUCCH and a PUSCH simultaneously. A pair of RBsin a subframe are allocated to a PUCCH for a UE. The RBs of the RB pairoccupy different subcarriers in two slots. Thus it is said that the RBpair frequency-hops over a slot boundary.

FIG. 5 illustrates a structure of a DL subframe that may be used inembodiments of the present disclosure.

Referring to FIG. 5, up to three OFDM symbols of a DL subframe, startingfrom OFDM symbol 0 are used as a control region to which controlchannels are allocated and the other OFDM symbols of the DL subframe areused as a data region to which a PDSCH is allocated. DL control channelsdefined for the 3GPP LTE system include a Physical Control FormatIndicator Channel (PCFICH), a PDCCH, and a Physical Hybrid ARQ IndicatorChannel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe,carrying information about the number of OFDM symbols used fortransmission of control channels (i.e. the size of the control region)in the subframe. The PHICH is a response channel to a UL transmission,delivering an HARQ ACK/NACK signal. Control information carried on thePDCCH is called Downlink Control Information (DCI). The DCI transportsUL resource assignment information, DL resource assignment information,or UL Transmission (Tx) power control commands for a UE group.

1.2 Physical Downlink Control Channel (PDCCH)

1.2.1 PDCCH Overview

The PDCCH may deliver information about resource allocation and atransport format for a Downlink Shared Channel (DL-SCH) (i.e. a DLgrant), information about resource allocation and a transport format foran Uplink Shared Channel (UL-SCH) (i.e. a UL grant), paging informationof a Paging Channel (PCH), system information on the DL-SCH, informationabout resource allocation for a higher-layer control message such as arandom access response transmitted on the PDSCH, a set of Tx powercontrol commands for individual UEs of a UE group, Voice Over InternetProtocol (VoIP) activation indication information, etc.

A plurality of PDCCHs may be transmitted in the control region. A UE maymonitor a plurality of PDCCHs. A PDCCH is transmitted in an aggregate ofone or more consecutive Control Channel Elements (CCEs). A PDCCH made upof one or more consecutive CCEs may be transmitted in the control regionafter subblock interleaving. A CCE is a logical allocation unit used toprovide a PDCCH at a code rate based on the state of a radio channel. ACCE includes a plurality of RE Groups (REGs). The format of a PDCCH andthe number of available bits for the PDCCH are determined according tothe relationship between the number of CCEs and a code rate provided bythe CCEs.

1.2.2 PDCCH Structure

A plurality of PDCCHs for a plurality of UEs may be multiplexed andtransmitted in the control region. A PDCCH is made up of an aggregate ofone or more consecutive CCEs. A CCE is a unit of 9 REGs each REGincluding 4 REs. Four Quadrature Phase Shift Keying (QPSK) symbols aremapped to each REG. REs occupied by RSs are excluded from REGs. That is,the total number of REGs in an OFDM symbol may be changed depending onthe presence or absence of a cell-specific RS. The concept of an REG towhich four REs are mapped is also applicable to other DL controlchannels (e.g. the PCFICH or the PHICH). Let the number of REGs that arenot allocated to the PCFICH or the PHICH be denoted by NREG. Then thenumber of CCEs available to the system is NCCE (=└N_(REG)/9┘) and theCCEs are indexed from 0 to NCCE−1.

To simplify the decoding process of a UE, a PDCCH format including nCCEs may start with a CCE having an index equal to a multiple of n. Thatis, given CCE i, the PDCCH format may start with a CCE satisfying i modn=0.

The eNB may configure a PDCCH with 1, 2, 4, or 8 CCEs. {1, 2, 4, 8} arecalled CCE aggregation levels. The number of CCEs used for transmissionof a PDCCH is determined according to a channel state by the eNB. Forexample, one CCE is sufficient for a PDCCH directed to a UE in a good DLchannel state (a UE near to the eNB). On the other hand, 8 CCEs may berequired for a PDCCH directed to a UE in a poor DL channel state (a UEat a cell edge) in order to ensure sufficient robustness.

[Table 2] below illustrates PDCCH formats. 4 PDCCH formats are supportedaccording to CCE aggregation levels as illustrated in [Table 2].

TABLE 2 Number of PDCCH format Number of CCE (n) Number of REG PDCCHbits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

A different CCE aggregation level is allocated to each UE because theformat or Modulation and Coding Scheme (MCS) level of controlinformation delivered in a PDCCH for the UE is different. An MCS leveldefines a code rate used for data coding and a modulation order. Anadaptive MCS level is used for link adaptation. In general, three orfour MCS levels may be considered for control channels carrying controlinformation.

Regarding the formats of control information, control informationtransmitted on a PDCCH is called DCI. The configuration of informationin PDCCH payload may be changed depending on the DCI format. The PDCCHpayload is information bits. [Table 3] lists DCI according to DCIformats.

TABLE 3 DCI Format Description Format 0 Resource grants for PUSCHtransmissions (uplink) Format 1 Resource assignments for single codewordPDSCH transmission (transmission modes 1, 2 and 7) Format 1A Compactsignaling of resource assignments for single codeword PDSCH (all modes)Format 1B Compact resource assignments for PDSCH using rank-1 closedloop preceding (mode 6) Format 1C Very compact resource assignments forPDSCH (e.g., paging/broadcast system information) Format 1D Compactresource assignments for PDSCH using multi-user MIMO(mode 5) Format 2Resource assignments for PDSCH for closed loop MIMO operation (mode 4)Format 2A resource assignments for PDSCH for open loop MIMO operation(mode 3) Format 3/3A Power control commands for PUCCH and PUSCH with2-bit/1-bit power adjustment Format 4 Scheduling of PUSCH in one UL cellwith multi-antenna port transmission mode

Referring to [Table 3], the DCI formats include Format 0 for PUSCHscheduling, Format 1 for single-codeword PDSCH scheduling, Format 1A forcompact single-codeword PDSCH scheduling, Format 1C for very compactDL-SCH scheduling, Format 2 for PDSCH scheduling in a closed-loopspatial multiplexing mode, Format 2A for PDSCH scheduling in anopen-loop spatial multiplexing mode, and Format 3/3A for transmission ofTransmission Power Control (TPC) commands for uplink channels. DCIFormat 1A is available for PDSCH scheduling irrespective of thetransmission mode of a UE.

The length of PDCCH payload may vary with DCI formats. In addition, thetype and length of PDCCH payload may be changed depending on compact ornon-compact scheduling or the transmission mode of a UE.

The transmission mode of a UE may be configured for DL data reception ona PDSCH at the UE. For example, DL data carried on a PDSCH includesscheduled data, a paging message, a random access response, broadcastinformation on a BCCH, etc. for a UE. The DL data of the PDSCH isrelated to a DCI format signaled through a PDCCH. The transmission modemay be configured semi-statically for the UE by higher-layer signaling(e.g. Radio Resource Control (RRC) signaling). The transmission mode maybe classified as single antenna transmission or multi-antennatransmission.

A transmission mode is configured for a UE semi-statically byhigher-layer signaling. For example, multi-antenna transmission schememay include transmit diversity, open-loop or closed-loop spatialmultiplexing, Multi-User Multiple Input Multiple Output (MU-MIMO), orbeamforming. Transmit diversity increases transmission reliability bytransmitting the same data through multiple Tx antennas. Spatialmultiplexing enables high-speed data transmission without increasing asystem bandwidth by simultaneously transmitting different data throughmultiple Tx antennas. Beamforming is a technique of increasing theSignal to Interference plus Noise Ratio (SINR) of a signal by weightingmultiple antennas according to channel states.

A DCI format for a UE depends on the transmission mode of the UE. The UEhas a reference DCI format monitored according to the transmission modeconfigure for the UE. The following 10 transmission modes are availableto UEs:

(1) Transmission mode 1: Single antenna port (port 0);

(2) Transmission mode 2: Transmit diversity;

(3) Transmission mode 3: Open-loop spatial multiplexing when the numberof layer is larger than 1 or Transmit diversity when the rank is 1;

(4) Transmission mode 4: Closed-loop spatial multiplexing;

(5) Transmission mode 5: MU-MIMO;

(6) Transmission mode 6: Closed-loop rank-1 precoding;

(7) Transmission mode 7: Precoding supporting a single layertransmission, which is not based on a codebook (Rel-8);

(8) Transmission mode 8: Precoding supporting up to two layers, whichare not based on a codebook (Rel-9);

(9) Transmission mode 9: Precoding supporting up to eight layers, whichare not based on a codebook (Rel-10); and

(10) Transmission mode 10: Precoding supporting up to eight layers,which are not based on a codebook, used for CoMP (Rel-11).

1.2.3 PDCCH Transmission

The eNB determines a PDCCH format according to DCI that will betransmitted to the UE and adds a Cyclic Redundancy Check (CRC) to thecontrol information. The CRC is masked by a unique Identifier (ID) (e.g.a Radio Network Temporary Identifier (RNTI)) according to the owner orusage of the PDCCH. If the PDCCH is destined for a specific UE, the CRCmay be masked by a unique ID (e.g. a cell-RNTI (C-RNTI)) of the UE. Ifthe PDCCH carries a paging message, the CRC of the PDCCH may be maskedby a paging indicator ID (e.g. a Paging-RNTI (P-RNTI)). If the PDCCHcarries system information, particularly, a System Information Block(SIB), its CRC may be masked by a system information ID (e.g. a SystemInformation RNTI (SI-RNTI)). To indicate that the PDCCH carries a randomaccess response to a random access preamble transmitted by a UE, its CRCmay be masked by a Random Access-RNTI (RA-RNTI).

Then, the eNB generates coded data by channel-encoding the CRC-addedcontrol information. The channel coding may be performed at a code ratecorresponding to an MCS level. The eNB rate-matches the coded dataaccording to a CCE aggregation level allocated to a PDCCH format andgenerates modulation symbols by modulating the coded data. Herein, amodulation order corresponding to the MCS level may be used for themodulation. The CCE aggregation level for the modulation symbols of aPDCCH may be one of 1, 2, 4, and 8. Subsequently, the eNB maps themodulation symbols to physical REs (i.e. CCE to RE mapping).

1.2.4 Blind Decoding (BD)

A plurality of PDCCHs may be transmitted in a subframe. That is, thecontrol region of a subframe includes a plurality of CCEs, CCE 0 to CCENCCE,k−1. NCCE,k is the total number of CCEs in the control region of akth subframe. A UE monitors a plurality of PDCCHs in every subframe.This means that the UE attempts to decode each PDCCH according to amonitored PDCCH format.

The eNB does not provide the UE with information about the position of aPDCCH directed to the UE in an allocated control region of a subframe.Without knowledge of the position, CCE aggregation level, or DCI formatof its PDCCH, the UE searches for its PDCCH by monitoring a set of PDCCHcandidates in the subframe in order to receive a control channel fromthe eNB. This is called blind decoding. Blind decoding is the process ofdemasking a CRC part with a UE ID, checking a CRC error, and determiningwhether a corresponding PDCCH is a control channel directed to a UE bythe UE.

The UE monitors a PDCCH in every subframe to receive data transmitted tothe UE in an active mode. In a Discontinuous Reception (DRX) mode, theUE wakes up in a monitoring interval of every DRX cycle and monitors aPDCCH in a subframe corresponding to the monitoring interval. ThePDCCH-monitored subframe is called a non-DRX subframe.

To receive its PDCCH, the UE should blind-decode all CCEs of the controlregion of the non-DRX subframe. Without knowledge of a transmitted PDCCHformat, the UE should decode all PDCCHs with all possible CCEaggregation levels until the UE succeeds in blind-decoding a PDCCH inevery non-DRX subframe. Since the UE does not know the number of CCEsused for its PDCCH, the UE should attempt detection with all possibleCCE aggregation levels until the UE succeeds in blind decoding of aPDCCH.

In the LTE system, the concept of Search Space (SS) is defined for blinddecoding of a UE. An SS is a set of PDCCH candidates that a UE willmonitor. The SS may have a different size for each PDCCH format. Thereare two types of SSs, Common Search Space (CSS) andUE-specific/Dedicated Search Space (USS).

While all UEs may know the size of a CSS, a USS may be configured foreach individual UE. Accordingly, a UE should monitor both a CSS and aUSS to decode a PDCCH. As a consequence, the UE performs up to 44 blinddecodings in one subframe, except for blind decodings based on differentCRC values (e.g., C-RNTI, P-RNTI, SI-RNTI, and RA-RNTI).

In view of the constraints of an SS, the eNB may not secure CCEresources to transmit PDCCHs to all intended UEs in a given subframe.This situation occurs because the remaining resources except forallocated CCEs may not be included in an SS for a specific UE. Tominimize this obstacle that may continue in the next subframe, aUE-specific hopping sequence may apply to the starting point of a USS.

[Table 4] illustrates the sizes of CSSs and USSs.

TABLE 4 PDCCH Number of Number of Number of Format CCE (n) candidates inCSS candidates in USS 0 1 — 6 1 2 — 6 2 4 4 2 3 8 2 2

To mitigate the load of the UE caused by the number of blind decodingattempts, the UE does not search for all defined DCI formatssimultaneously. Specifically, the UE always searches for DCI Format 0and DCI Format 1A in a USS. Although DCI Format 0 and DCI Format 1A areof the same size, the UE may distinguish the DCI formats by a flag forformat0/format 1a differentiation included in a PDCCH. Other DCI formatsthan DCI Format 0 and DCI Format 1A, such as DCI Format 1, DCI Format1B, and DCI Format 2 may be required for the UE.

The UE may search for DCI Format 1A and DCI Format 1C in a CSS. The UEmay also be configured to search for DCI Format 3 or 3A in the CSS.Although DCI Format 3 and DCI Format 3A have the same size as DCI Format0 and DCI Format 1A, the UE may distinguish the DCI formats by a CRCscrambled with an ID other than a UE-specific ID.

An SS S_(k) ^((L)) is a PDCCH candidate set with a CCE aggregation levelLε{1,2,4,8}. The CCEs of PDCCH candidate set m in the SS may bedetermined by the following equation.

L·{(Y _(k) +m)mod └N _(CCE,k) /L┘}+i  [Equation 1]

Herein, M^((L)) is the number of PDCCH candidates with CCE aggregationlevel L to be monitored in the SS, m=0, . . . , M^((L))−1, i is theindex of a CCE in each PDCCH candidate, and i=0, . . . , L−1.k=└n_(s)/2┘ where n_(s) is the index of a slot in a radio frame.

As described before, the UE monitors both the USS and the CSS to decodea PDCCH. The CSS supports PDCCHs with CCE aggregation levels {4, 8} andthe USS supports PDCCHs with CCE aggregation levels {1, 2, 4, 8}. [Table5] illustrates PDCCH candidates monitored by a UE.

TABLE 5 Search space S_(k) ^((L)) Number of PDCCH Type Aggregation levelL Size [in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 162 Common 4 16 4 8 16 2

Referring to [Equation 1], for two aggregation levels, L=4 and L=8,Y_(k) is set to 0 in the CSS, whereas Y_(k) is defined by [Equation 2]for aggregation level L in the USS.

Y _(k)=(A·Y _(k-1))mod D  [Equation 2]

Herein, Y⁻¹=n_(RNTI)≠0, n_(RNTI) indicating an RNTI value. A=39827 andD=65537.

1.3 Carrier Aggregation (CA) Environment

1.3.1 CA Overview

A 3GPP LTE system (conforming to Rel-8 or Rel-9) (hereinafter, referredto as an LTE system) uses Multi-Carrier Modulation (MCM) in which asingle Component Carrier (CC) is divided into a plurality of bands. Incontrast, a 3GPP LTE-A system (hereinafter, referred to an LTE-A system)may use CA by aggregating one or more CCs to support a broader systembandwidth than the LTE system. The term CA is interchangeably used withcarrier combining, multi-CC environment, or multi-carrier environment.

In the present disclosure, multi-carrier means CA (or carriercombining). Herein, CA covers aggregation of contiguous carriers andaggregation of non-contiguous carriers. The number of aggregated CCs maybe different for a DL and a UL. If the number of DL CCs is equal to thenumber of UL CCs, this is called symmetric aggregation. If the number ofDL CCs is different from the number of UL CCs, this is called asymmetricaggregation. The term CA is interchangeable with carrier combining,bandwidth aggregation, spectrum aggregation, etc.

The LTE-A system aims to support a bandwidth of up to 100 MHz byaggregating two or more CCs, that is, by CA. To guarantee backwardcompatibility with a legacy IMT system, each of one or more carriers,which has a smaller bandwidth than a target bandwidth, may be limited toa bandwidth used in the legacy system.

For example, the legacy 3GPP LTE system supports bandwidths {1.4, 3, 5,10, 15, and 20 MHz} and the 3GPP LTE-A system may support a broaderbandwidth than 20 MHz using these LTE bandwidths. A CA system of thepresent disclosure may support CA by defining a new bandwidthirrespective of the bandwidths used in the legacy system.

There are two types of CA, intra-band CA and inter-band CA. Intra-bandCA means that a plurality of DL CCs and/or UL CCs are successive oradjacent in frequency. In other words, the carrier frequencies of the DLCCs and/or UL CCs are positioned in the same band. On the other hand, anenvironment where CCs are far away from each other in frequency may becalled inter-band CA. In other words, the carrier frequencies of aplurality of DL CCs and/or UL CCs are positioned in different bands. Inthis case, a UE may use a plurality of Radio Frequency (RF) ends toconduct communication in a CA environment.

The LTE-A system adopts the concept of cell to manage radio resources.The above-described CA environment may be referred to as a multi-cellenvironment. A cell is defined as a pair of DL and UL CCs, although theUL resources are not mandatory. Accordingly, a cell may be configuredwith DL resources alone or DL and UL resources.

For example, if one serving cell is configured for a specific UE, the UEmay have one DL CC and one UL CC. If two or more serving cells areconfigured for the UE, the UE may have as many DL CCs as the number ofthe serving cells and as many UL CCs as or fewer UL CCs than the numberof the serving cells, or vice versa. That is, if a plurality of servingcells are configured for the UE, a CA environment using more UL CCs thanDL CCs may also be supported.

CA may be regarded as aggregation of two or more cells having differentcarrier frequencies (center frequencies). Herein, the term ‘cell’ shouldbe distinguished from ‘cell’ as a geographical area covered by an eNB.Hereinafter, intra-band CA is referred to as intra-band multi-cell andinter-band CA is referred to as inter-band multi-cell.

In the LTE-A system, a Primacy Cell (PCell) and a Secondary Cell (SCell)are defined. A PCell and an SCell may be used as serving cells. For a UEin RRC_CONNECTED state, if CA is not configured for the UE or the UEdoes not support CA, a single serving cell including only a PCell existsfor the UE. On the contrary, if the UE is in RRC_CONNECTED state and CAis configured for the UE, one or more serving cells may exist for theUE, including a PCell and one or more SCells.

Serving cells (PCell and SCell) may be configured by an RRC parameter. Aphysical-layer ID of a cell, PhysCellId is an integer value ranging from0 to 503. A short ID of an SCell, SCellIndex is an integer value rangingfrom 1 to 7. A short ID of a serving cell (PCell or SCell),ServeCellIndex is an integer value ranging from 1 to 7. IfServeCellIndex is 0, this indicates a PCell and the values ofServeCellIndex for SCells are pre-assigned. That is, the smallest cellID (or cell index) of ServeCellIndex indicates a PCell.

A PCell refers to a cell operating in a primary frequency (or a primaryCC). A UE may use a PCell for initial connection establishment orconnection reestablishment. The PCell may be a cell indicated duringhandover. In addition, the PCell is a cell responsible forcontrol-related communication among serving cells configured in a CAenvironment. That is, PUCCH allocation and transmission for the UE maytake place only in the PCell. In addition, the UE may use only the PCellin acquiring system information or changing a monitoring procedure. AnEvolved Universal Terrestrial Radio Access Network (E-UTRAN) may changeonly a PCell for a handover procedure by a higher-layerRRCConnectionReconfiguraiton message including mobilityControlInfo to aUE supporting CA.

An SCell may refer to a cell operating in a secondary frequency (or asecondary CC). Although only one PCell is allocated to a specific UE,one or more SCells may be allocated to the UE. An SCell may beconfigured after RRC connection establishment and may be used to provideadditional radio resources. There is no PUCCH in cells other than aPCell, that is, in SCells among serving cells configured in the CAenvironment.

When the E-UTRAN adds an SCell to a UE supporting CA, the E-UTRAN maytransmit all system information related to operations of related cellsin RRC_CONNECTED state to the UE by dedicated signaling. Changing systeminformation may be controlled by releasing and adding a related SCell.Herein, a higher-layer RRCConnectionReconfiguration message may be used.The E-UTRAN may transmit a dedicated signal having a different parameterfor each cell rather than it broadcasts in a related SCell.

After an initial security activation procedure starts, the E-UTRAN mayconfigure a network including one or more SCells by adding the SCells toa PCell initially configured during a connection establishmentprocedure. In the CA environment, each of a PCell and an SCell mayoperate as a CC. Hereinbelow, a Primary CC (PCC) and a PCell may be usedin the same meaning and a Secondary CC (SCC) and an SCell may be used inthe same meaning in embodiments of the present disclosure.

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, whichare used in embodiments of the present disclosure.

FIG. 6(a) illustrates a single carrier structure in the LTE system.There are a DL CC and a UL CC and one CC may have a frequency range of20 MHz.

FIG. 6(b) illustrates a CA structure in the LTE-A system. In theillustrated case of FIG. 6(b), three CCs each having 20 MHz areaggregated. While three DL CCs and three UL CCs are configured, thenumbers of DL CCs and UL CCs are not limited. In CA, a UE may monitorthree CCs simultaneously, receive a DL signal/DL data in the three CCs,and transmit a UL signal/UL data in the three CCs.

If a specific cell manages N DL CCs, the network may allocate M (M≦N) DLCCs to a UE. The UE may monitor only the M DL CCs and receive a DLsignal in the M DL CCs. The network may prioritize L (L≦M≦N) DL CCs andallocate a main DL CC to the UE. In this case, the UE should monitor theL DL CCs. The same thing may apply to UL transmission.

The linkage between the carrier frequencies of DL resources (or DL CCs)and the carrier frequencies of UL resources (or UL CCs) may be indicatedby a higher-layer message such as an RRC message or by systeminformation. For example, a set of DL resources and UL resources may beconfigured based on linkage indicated by System Information Block Type 2(SIB2). Specifically, DL-UL linkage may refer to a mapping relationshipbetween a DL CC carrying a PDCCH with a UL grant and a UL CC using theUL grant, or a mapping relationship between a DL CC (or a UL CC)carrying HARQ data and a UL CC (or a DL CC) carrying an HARQ ACK/NACKsignal.

1.3.2 Cross Carrier Scheduling

Two scheduling schemes, self-scheduling and cross carrier scheduling aredefined for a CA system, from the perspective of carriers or servingcells. Cross carrier scheduling may be called cross CC scheduling orcross cell scheduling.

In self-scheduling, a PDCCH (carrying a DL grant) and a PDSCH aretransmitted in the same DL CC or a PUSCH is transmitted in a UL CClinked to a DL CC in which a PDCCH (carrying a UL grant) is received.

In cross carrier scheduling, a PDCCH (carrying a DL grant) and a PDSCHare transmitted in different DL CCs or a PUSCH is transmitted in a UL CCother than a UL CC linked to a DL CC in which a PDCCH (carrying a ULgrant) is received.

Cross carrier scheduling may be activated or deactivated UE-specificallyand indicated to each UE semi-statically by higher-layer signaling (e.g.RRC signaling).

If cross carrier scheduling is activated, a Carrier Indicator Field(CIF) is required in a PDCCH to indicate a DL/UL CC in which aPDSCH/PUSCH indicated by the PDCCH is to be transmitted. For example,the PDCCH may allocate PDSCH resources or PUSCH resources to one of aplurality of CCs by the CIF. That is, when a PDCCH of a DL CC allocatesPDSCH or PUSCH resources to one of aggregated DL/UL CCs, a CIF is set inthe PDCCH. In this case, the DCI formats of LTE Release-8 may beextended according to the CIF. The CIF may be fixed to three bits andthe position of the CIF may be fixed irrespective of a DCI format size.In addition, the LTE Release-8 PDCCH structure (the same coding andresource mapping based on the same CCEs) may be reused.

On the other hand, if a PDCCH transmitted in a DL CC allocates PDSCHresources of the same DL CC or allocates PUSCH resources in a single ULCC linked to the DL CC, a CIF is not set in the PDCCH. In this case, theLTE Release-8 PDCCH structure (the same coding and resource mappingbased on the same CCEs) may be used.

If cross carrier scheduling is available, a UE needs to monitor aplurality of PDCCHs for DCI in the control region of a monitoring CCaccording to the transmission mode and/or bandwidth of each CC.Accordingly, an appropriate SS configuration and PDCCH monitoring areneeded for the purpose.

In the CA system, a UE DL CC set is a set of DL CCs scheduled for a UEto receive a PDSCH, and a UE UL CC set is a set of UL CCs scheduled fora UE to transmit a PUSCH. A PDCCH monitoring set is a set of one or moreDL CCs in which a PDCCH is monitored. The PDCCH monitoring set may beidentical to the UE DL CC set or may be a subset of the UE DL CC set.The PDCCH monitoring set may include at least one of the DL CCs of theUE DL CC set. Or the PDCCH monitoring set may be defined irrespective ofthe UE DL CC set. DL CCs included in the PDCCH monitoring set may beconfigured to always enable self-scheduling for UL CCs linked to the DLCCs. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring setmay be configured UE-specifically, UE group-specifically, orcell-specifically.

If cross carrier scheduling is deactivated, this implies that the PDCCHmonitoring set is always identical to the UE DL CC set. In this case,there is no need for signaling the PDCCH monitoring set. However, ifcross carrier scheduling is activated, the PDCCH monitoring set may bedefined within the UE DL CC set. That is, the eNB transmits a PDCCH onlyin the PDCCH monitoring set to schedule a PDSCH or PUSCH for the UE.

FIG. 7 illustrates a cross carrier-scheduled subframe structure in theLTE-A system, which is used in embodiments of the present disclosure.

Referring to FIG. 7, three DL CCs are aggregated for a DL subframe forLTE-A UEs. DL CC ‘A’ is configured as a PDCCH monitoring DL CC. If a CIFis not used, each DL CC may deliver a PDCCH that schedules a PDSCH inthe same DL CC without a CIF. On the other hand, if the CIF is used byhigher-layer signaling, only DL CC ‘A’ may carry a PDCCH that schedulesa PDSCH in the same DL CC ‘A’ or another CC. Herein, no PDCCH istransmitted in DL CC ‘B’ and DL CC ‘C’ that are not configured as PDCCHmonitoring DL CCs.

1.3.3 CA Environment-Based CoMP Operation

Hereinafter, a cooperation multi-point (CoMP) transmission operationapplicable to the embodiments of the present disclosure will bedescribed.

In the LTE-A system, CoMP transmission may be implemented using acarrier aggregation (CA) function in the LTE. FIG. 8 is a conceptualview illustrating a CoMP system operating based on a CA environment.

In FIG. 8, it is assumed that a carrier operated as a PCell and acarrier operated as an SCell may use the same frequency band on afrequency axis and are allocated to two eNBs geographically spaced apartfrom each other. At this time, a serving eNB of UE1 may be allocated tothe PCell, and a neighboring cell causing much interference may beallocated to the SCell. That is, the eNB of the PCell and the eNB of theSCell may perform various DL/UL CoMP operations such as jointtransmission (JT), CS/CB and dynamic cell selection for one UE.

FIG. 8 illustrates an example that cells managed by two eNBs areaggregated as PCell and SCell with respect to one UE (e.g., UE1).However, as another example, three or more cells may be aggregated. Forexample, some cells of three or more cells may be configured to performCoMP operation for one UE in the same frequency band, and the othercells may be configured to perform simple CA operation in differentfrequency bands. At this time, the PCell does not always need toparticipate in CoMP operation.

1.4 System Information Block (SIB)

SIBs are used for an eNB to transmit system information. That is, a UEmay acquire system information by receiving different SIBs from the eNB.The SIBs are transmitted on a DL-SCH at the logical layer, and on aPDSCH at the physical layer. It is determined whether there is an SIB,by a PDCCH signal masked with a System Information Radio NetworkTemporary Identifier (SI-RNTI).

Among the SIBs, SIB type 1 (SIB1) includes parameters required todetermine whether a corresponding cell is suitable for cell selection,and information about time-axis scheduling of other SIBs. SIB type 2(SIB2) includes common channel information and shared channelinformation. SIB3 to SIB8 include cell reselection-related information,inter-frequency information, intra-frequency information, and so on.SIB9 is used to indicate the name of a Home eNode B (HeNB), and SIB10,SIB11, and SIB12 include an Earthquake and Tsunami Warning Service(ETWS) notification and a Commercial Mobile Alert System (CMAS) alertmessage. SIB13 includes Multimedia Broadcast Multicast Service(MBMS)-related control information.

Herein, SIB1 includes cell access-related parameters and schedulinginformation about other SIBs. SIB1 is transmitted every 80 ms, and a UEshould be able to receive SIB1 in idle mode/connected mode. SIB1 istransmitted every 80 ms, and a UE should be able to receive SIB1 in idlemode/connected mode. Transmission of SIB1 starts in subframe #5 of aradio frame satisfying SFN mod 8=0 and proceeds in subframe #5 of aradio frame satisfying SFN mod 2=0. SIB1 is transmitted, including thefollowing information.

TABLE 6 SystemInformationBlockType1 := SEQUENCE { cellAccessRelatedInfoSEQUENCE { plmn-IdentityList PLMN-IdentityList, trackingAreaCodeTrackingAreaCode, cellIdentity CellIdentity, cellBarred ENUMERATED{barred, notBarred}, intraFreqReselection ENUMERATED {allowed,notAllowed}. csg-Indication BOOLEAN, csg-Identity CSG-Identity OPTIONAL-- Need OR }, cellSelectionInfo SEQUENCE { q-RxLevMin Q-RxLevMin,q-RxLevMinOffset INTEGER (1..8) OPTIONAL -- Need OP }. p-Max P-MaxOPTIONAL, -- Need OP freqBandIndicator FreqBandIndicator,schedulingInfoList SchedulingInfoList, tdd-Config TDD-Config OPTIONAL,-- Cond TDD si-WindowLength ENUMERATED { ms1, ms2, ms5, ms10, ms15,ms20, ms40}, systemInfoValueTag INTEGER (0..31), nonCriticalExtensionSystemInformationBlockType1-v890-IEs OPTIONAL } SchedulingInfoList ::=SEQUENCE (SIZE (1..maxSI-Message)) OF SchedulingInfo SchedulingInfo ::=SEQUENCE { si-Periodicity ENUMERATED { rf8, rf16, rf32, rf64, rf128,rf256, rf512}, sib-MappingInfo SIB-MappingInfo } SIB-MappingInfo ::=SEQUENCE (SIZE (0..maxSIB-1)) OF SIB-Type SIB-Type ::= ENUMERATED { sibType3, sibType4, sibType5, sibType6,  sibType7, sibType8, sibType9,sibType10,  sibType11, sibType12-v920, sibType13-v920,  sibType14-v1130,sibType15-v1130,  sibType16-v1130, sibType17-v12xy, spare1, ...}

For a description of the parameters included in SIB1, as listed in[Table 6], refer to sub-clauses 5.2.2.7 and 6.2.2 of 3GPP TS 36.331.

SI messages may be transmitted within a time area (i.e., an SI window)generated periodically by dynamic scheduling. Each SI message is relatedto a specific SI window, and the specific SI windows do not overlap withother SI messages. A common SI window length may be set for all SImessages.

Within an SI window, a corresponding SI message is transmitted aplurality of times in all subframes except for MBSFN subframes, and ULsubframes and subframes #5 of radio frames satisfying SFN mod 2=0 inTDD. A UE may acquire specific time-domain scheduling information fromSI messages.

RVs are determined for a PDSCH scheduled by a PDCCH masked with anSI-RNTI in DCI format 1C, according to the following [Equation 3].

RV_(K)=ceiling(3/2*k)modulo 4  [Equation 3]

In [Equation 3], k is determined according to the type of an SI message.For example, k=(SFN/2) modulo 4 for an SIB1 message. Here, SFNrepresents a system frame number. For each piece of system information,k=i modulo 4 and i=0, 1, . . . , n_(s) ^(w)−1 where i represents thenumber of a subframe within an SI window n_(s) ^(w).

1.5 Method for Transmitting Paging Message

A paging message is used to deliver paging information, SI messageupdate information, a Public Warning System (PWS) message, or the like.A default paging cycle may be set for each cell and a dedicated pagingcycle may be set for each UE, for transmission of a paging message. Iftwo or more paging cycles are set for a UE, a minimum paging cyclebecomes the paging cycle of the UE.

Paging subframes available for transmission of a paging message may becalculated by [Equation 4].

SFN mod T=(T/N)×(UE_ID mod N)  [Equation 4]

In embodiments of the present disclosure, i_s represents an indexindicating a predefined table that defines paging subframes, andi_s=floor(UE_ID/N) mod N_(S). In [Equation 4], T is the UE DiscontinuousReception (DRX) cycle of the UE and may be given as T=min(T_(c),T_(UE))where T_(c) is a cell-specific default paging cycle which may be set to{32, 64, 128, 256} radio frames, and T_(UE) is a UE-specific pagingcycle which may be set to {32, 64, 128, 256} radio frames. N representsthe number of paging frames within one paging cycle, and may be given asN=min(T, nB) where nB is the number of paging subframes per paging cycle{4T, 2T, T, T/2, T/4, T/8, T/16, T/32}. N_(S) represents the number ofpaging subframes in a radio frame used for paging and it is configuredthat N_(s)=max(1, nB/T).

[Table 7] and [Table 8] below illustrate paging subframe patterns in FDDand TDD, respectively.

TABLE 7 PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s =3 1 9 N/A N/A N/A 2 4 9 N/A N/A 4 0 4 5 9

TABLE 8 PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s =3 1 0 N/A N/A N/A 2 0 5 N/A N/A 4 0 1 5 6

[Table 9] illustrates exemplary paging subframes determined according to[Equation 4] and paging-related parameters.

TABLE 9 Case UE_ID T_(c) T_(UE) T nB N N_(s) PF i_s PO A 147 256 256 25664 64 1 76 0 9 B 147 256 128 128 32 32 1 76 0 9 C 147 256 128 128 256128 2 19 1 4

1.6 Reference Signal (RS)

Now, a description will be given of RSs that may be used in embodimentsof the present disclosure.

FIG. 9 is a view illustrating an exemplary subframe in whichCell-specific Reference Signals (CRSs) are allocated, which may be usedin embodiments of the present disclosure.

FIG. 9 illustrates a CRS allocation structure, when a system supportsfour antennas. CRS is used for the purpose of decoding and channel statemeasurement in the 3GPP LTE/LTE-A system. Therefore, CRSs aretransmitted across a total DL bandwidth in every DL subframe in a cellsupporting PDSCH transmission, and through all antenna ports configuredfor an eNB.

Specifically, a CRS sequence is mapped to complex-valued modulationsymbols used as reference symbols for antenna port p in slot n_(s).

A UE may measure CSI using CRSs and decode a DL data signal received ona PDSCH in a subframe including CRSs, using the CRSs. That is, the eNBtransmits CRSs at predetermined positions in every RB, and the UEperforms channel estimation based on the CRSs and then detects thePDSCH. For example, the UE measures signals received in CRS REs. The UEmay detect a PDSCH signal in REs to which the PDSCH is mapped, based onthe ratio between per-CRS RE reception energy and per-PDSCH RE receptionenergy.

If a PDSCH signal is transmitted based on CRSs in this manner, the eNBshould transmit CRSs in all RBs, resulting in unnecessary RS overhead.To solve the problem, the 3GPP LTE-A system additionally definesUE-specific RS (hereinafter, referred to as UE-RS) and Channel StateInformation Reference Signal (CSI-RS) as well as CRS. UE-RS is used fordemodulation, and CSI-RS is used for deriving CSI.

Since UE-RS and CRS are used for demodulation, they may be referred toas demodulation RS in terms of their usage. That is, UE-RS may beregarded as a kind of Demodulation Reference Signal (DM-RS). Further,since CSI-RS and CRS are used for channel measurement or channelestimation, they may be regarded as channel state measurement RS interms of their usage.

FIG. 10 is a view illustrating exemplary subframes in which CSI-RSs areallocated according to numbers of antenna ports, which may be used inembodiments of the present disclosure.

CSI-RS is a DL RS which has been introduced to the 3GPP LTE-A system,for the purpose of radio channel state measurement, not demodulation.The 3GPP LTE-A system defines a plurality of CSI-RS configurations forCSI-RS transmission. A CSI-RS sequence is mapped to complex-valuedmodulation symbols used as reference symbols for antenna port p insubframes for which CSI-RS transmission is configured.

FIG. 10(a) illustrates 20 CSI-RS configurations, CSI-RS configuration 0to CSI-RS configuration 19 available for CSI-RS transmission through 2CSI ports, among CSI-RS configuration, FIG. 10(b) illustrates 10 CSI-RSconfigurations, CSI-RS configuration 0 to CSI-RS configuration 9available for CSI-RS transmission through 4 CSI ports, among the CSI-RSconfigurations, and FIG. 10(c) illustrates 5 CSI-RS configurations,CSI-RS configuration 0 to CSI-RS configuration 4 available for CSI-RStransmission through 8 CSI ports, among the CSI-RS configurations.

Herein, a CSI-RS port refers to an antenna port configured for CSI-RStransmission. A different CSI-RS configuration is used according to thenumber of CSI-RS ports. Therefore, in spite of the same CSI-RSconfiguration number, the CSI-RS configuration is different for adifferent number of antenna ports configured for CSI-RS transmission.

Compared to CRSs configured to be transmitted in every subframe, CSI-RSsare configured to be transmitted in every predetermined transmissionperiod corresponding to a plurality of subframes. Accordingly, theCSI-RS configuration differs according to a subframe for which CSI-RSsare configured as well as the positions of REs occupied by CSI-RSs in anRB pair.

Despite the same CSI-RS configuration number, the CSI-RS configurationmay be considered to be different in a different subframe for CSI-RStransmission. For example, if ae CSI-RS transmission period T_(CSI-RS)is different or a starting subframe Δ_(CSI-RS) in which CSI-RStransmission is configured in a radio frame is different, the CSI-RSconfiguration may be considered to be different.

In order to distinguish (1) a CSI-RS configuration to which a CSI-RSconfiguration number is assigned from (2) a CSI-RS configuration whichvaries according to a CSI-RS configuration number, the number of CSI-RSports, and/or a subframe for which CSI-RSs are configured, the latterCSI-RS configuration (2) will be referred to as a CSI-RS resourceconfiguration, and the former CSI-RS configuration (1) will be referredto as a CSI-RS configuration or a CSI-RS pattern.

When the eNB indicates a CSI-RS resource configuration to a UE, the eNBmay transmit to the UE information about the number of antenna portsused for transmission of CSI-RSs, a CSI-RS pattern, a CSI-RS subframeconfiguration I_(CSI-RS), a UE assumption on reference PDSCHtransmission power for CSI feedback, P_(c), a Zero Power (ZP) CSI-RSconfiguration list, a ZP CSI-RS subframe configuration, and so on.

The index of a CSI-RS subframe configuration, I_(CSI-RS) is informationthat specifies a subframe configuration periodicity T_(CSI-RS) foroccurrence of CSI-RSs, and a subframe offset Δ_(CSI-RS). [Table 10]below lists exemplary CSI-RS subframe configuration indexes, I_(CSI-RS)according to T_(CSI-RS) and Δ_(CSI-RS).

TABLE 10 CSI-RS-SubframeConfig CSI-RS periodicity CSI-RS subframe offsetI_(CSI-RS) T_(CSI-RS) (subframes) Δ_(CSI-RS) (subframes) 0-4 5I_(CSI-RS)  5-14 10 I_(CSI-RS) − 5  15-34 20 I_(CSI-RS) − 15 35-74 40I_(CSI-RS) − 35  75-154 80 I_(CSI-RS) − 75

Subframes satisfying [Equation 5] are CSI-RS subframes.

(10n _(f) +└n _(s)/2┘−Δ_(CSI-RS))mod T _(CSI-RS)  [Equation 5]

A UE for which a Transmission Mode (TM) defined beyond 3GPP LTE-A (e.g.,TM9 or a newly defined TM) has been configured may perform channelmeasurement using CSI-RSs, and decode a PDSCH using UE-RSs.

A UE for which a Transmission Mode (TM) defined beyond 3GPP LTE-A (e.g.,TM9 or a newly defined TM) has been configured may perform channelmeasurement using CSI-RSs, and decode a PDSCH using UE-RSs.

1.7 Enhanced PDCCH (EPDCCH)

In Cross-Carrier Scheduling (CCS) under a situation in which a pluralityof Components Carriers (CCs=(serving) cells) are aggregated in the 3GPPLTE/LTE-A system, one scheduled CC may be pre-configured to beDL/UL-scheduled only by one other scheduling CC (i.e., so that a DL/ULgrant PDCCH for the scheduled CC may be received). Basically, thescheduling CC may perform DL/UL scheduling for itself. In other words, aSearch Space (SS) for a PDCCH that schedules a scheduling/scheduled CCin the CCS relationship may exist in the control channel region of everyscheduling CC.

Meanwhile, the LTE system allocates the first n (n<=4) OFDM symbols ofeach subframe to transmission of physical channels, PDCCH, PHICH, andPCFICH carrying control information and allocates the other OFDM symbolsof the subframe to PDSCH transmission in an FDD DL carrier or TDD DLsubframes. The number of OFDM symbols used for transmission of controlchannels in each subframe may be indicated to UEs, dynamically on aphysical channel such as the PCFICH or semi-statically by RRC signaling.

A physical channel used for DL/UL scheduling and transmission of varioustypes of control information, PDCCH has limitations such as transmissionin limited OFDM symbols in the LTE/LTE-A system. Therefore, an extendedPDCCH (i.e., EPDCCH) multiplexed more freely with a PDSCH in FrequencyDivision Multiplexing (FDM)/Time Division Multiplexing (TDM) may beintroduced, instead of a control channel such as the PDCCH transmittedin OFDM symbols separate from PDSCH symbols. FIG. 11 is a viewillustrating exemplary multiplexing of the legacy PDCCH, the PDSCH, andthe EPDCCH in the LTE/LTE-A system.

2. Improved MTC Coverage

2.1 MTC UE

For an LTE-A system (beyond Rel-12) as a future-generation wirelesscommunication system, it is under consideration to configurelow-price/low-specification UEs that conduct mainly data communicationsuch as metering, water level measurement, use of a surveillance camera,and stock reporting of a vendor machine. In embodiments of the presentdisclosure, such UEs will be referred to as MTC UEs.

MTC is a scheme of conducting communication between devices withouthuman intervention. Smart metering may be considered to be a majorapplication of MTC. Smart metering is an application technology ofattaching a communication module to a metering device for measurement ofelectricity, gas, water, and so on, and transmitting measurementinformation periodically to a central control center or a datacollection center.

Further, since MTC UEs are supposed to be produced and distributed atlow prices, the MTC UEs may be designed to support only a very narrowband (e.g., equal to or less than 1RB, 2RBs, 3RBs, 4RBs, 5RBs, or 6RBs),compared to a general cellular system. In this case, an MTC UE is notcapable of decoding a DL control channel region transmitted across atotal system band as is done in the general cellular system, and controlinformation for the MTC UE may not be transmitted in the DL controlchannel region. That is why the amount of control information for an MTCUE is decreased and the amount of resources for data transmission to theMTC UE is also decreased.

An MTC UE used for smart metering may have difficulty in communicatingwith an eNB because the MTC UE is highly likely to be installed in ashadowing area such as a basement. Accordingly, data needs to betransmitted repeatedly on a DL channel and/or a UL channel to overcomethe difficulty. For example, the PDCCH/EPDCCH, PDSCH, PUSCH, and PUCCHmay all be transmitted repeatedly.

To realize low-price MTC UEs, the bandwidth of the MTC UEs may belimited. That is, although a system bandwidth is 10 MHz, an MTC UE maytransmit and receive signals only in 1.4 MHz. The present disclosureproposes a method for transmitting and receiving a Positioning ReferenceSignal (PRS) in a PRS subframe, a method for transmitting and receivinga PDSCH, and an operation of an MTC UE. Unless otherwise specified, thefollowing embodiments of the present disclosure may be implemented basedon the description of clause 1.

2.2 Method for Improving MTC Coverage

Now, a description will be given of methods for improving coverage forMTC UEs.

2.2.1 TTI Bundling/HARQ Retransmission/Repeated Transmission/CodeSpreading/RLC Segmentation/Low Rate Coding/Low Modulation Order/NewDecoding Techniques

For MTC UEs, more energy may be accumulated to improve coverage byprolonging a transmission time. For example, the existing TTI bundlingand HARQ retransmission in a data channel may be effective to MTC UEs.Since the current maximum number of UL HARQ retransmissions is 28 andTTI bundling is up to 4 consecutive subframes, TTI bundling with alarger TTI bundle size may be considered and the maximum number of HARQretransmissions may be increased, to achieve better performance. Asidefrom TTI bundling and HARQ retransmission, the same or different RVs maybe applied to repeated transmissions of data. In addition, codespreading in the time domain may also be considered to improve coverage.

MTC traffic packets may be RLC-segmented into smaller packets, and verylow rate coding, a lower modulation order (e.g., BPSK), and ashorter-length CRC may also be used.

New decoding techniques (e.g. correlation or reduced SS decoding) may beused to improve coverage by taking into account the characteristics ofparticular channels (e.g., a channel periodicity, a parameter changerate, a channel structure, limited content, etc.).

2.2.2 Power Boosting/Power Density Spectrum (PDS) Boosting

The eNB may transmit, to an MTC UE, DL data with more power (i.e., powerboosting), or at a given power level in a reduced bandwidth (i.e., PSDboosting). The application of power boosting or PSD boosting depends onthe channel or signal under consideration.

2.2.3 Relaxed Requirement

The performance requirements for some channels may be relaxedconsidering the characteristics (e.g., greater delay tolerance) of MTCUEs in extreme scenarios. For the Synchronization Signal (SS), MTC UEsmay accumulate energy by combining Primary SS (PSS) or Secondary SS(SSS) a plurality of times, but this will prolong an acquisition time.For a PRACH, a loosened PRACH detection threshold rate and a higherfalse alarm rate at the eNB may be considered.

2.2.4 Design of New Channel or Signal

New design of channels or signals for better coverage is possible ifimplementation-based schemes cannot meet coverage improvementrequirements. These channels and signals, together with other possiblelink-level solutions for coverage enhancement will be described below.

2.2.5 Small Cell for Coverage Improvement

Coverage enhancements using link improvements are preferably providedfor scenarios in which no small cells have been deployed by an operator.That is, an operator may deploy traditional coverage improvementsolutions using small cells (including Pico, Femto, Remote Radio Heads(RRHs), relays, repeaters, etc.) to provide coverage enhancements to MTCUEs and non-MTC UEs alike. In deployments of small cells, a path lossfrom a UE to the closest cell is reduced. As a result, for MTC UEs, arequired link budget may be reduced for all channels. Depending on thesmall cell location/density, the coverage enhancement may still berequired.

For eNB deployments that already contain small cells, there may be abenefit to further allow decoupled UL and DL for delay-tolerant MTC UEs.For UL, the best serving cell is chosen based on a least coupling loss.For DL, due to large transmission power imbalance (including antennagains) between a macro cell and a Low Power Node (LPN), the best servingcell is one with a maximum received signal power. This UL/DL decoupledassociation is feasible for MTC traffic especially for services withouttight delay requirements.

To enable a UL/DL decoupled operation either in a UE-transparent ornon-transparent manner, a macro serving cell and potential LPNs may needto exchange information for channel (e.g. RACH, PUSCH, and SRS)configurations and to identify a suitable LPN. A different RACHconfiguration from that of non-decoupled UL/DL may be needed fordecoupled UL/DL.

Possible link-level solutions for coverage enhancement of variousphysical channels and signals are summarized in [Table 11].

TABLE 11 Channels PDSCH/ Signals Solutions PSS/SSS PBCH PRACH (E)PDCCHPUSCH PUCCH PSD boosting x x x x x Relaxed requirement x x Design newchannels/signals x x x x x Repetition x x x x x Low rate coding x x x xTTI bundling/Retransmission x Spreading x x RS power boosting/in- x x xcreased RS density New decoding techniques x

3. Method for Transmitting Common Control Message for MTC UEs

When a UE initially accesses a specific serving cell, the UE receives,from an eNodeB managing and controlling the serving cell, a MasterInformation Block (MIB) for the serving cell on a PBCH, and an SIBmessage and RRC parameters on a PDSCH. Further, the UE may receive apaging message to receive changed system information or paginginformation.

Since an MTC UE may be installed in an area (e.g., a basement) under apoor transmission environment, compared to a legacy UE, if the eNodeBtransmits an SIB message to the MTC UE and the legacy UE in the samemanner, the MTC UE may have difficulty in receiving the SIB message. Tosolve the problem, in the case where the eNodeB transmits an SIB orpaging message on a PDSCH to an MTC UE facing such a coverage issue, theeNodeB may transmit the SIB or paging message by applying a coverageenhancement technique such as subframe repetition or subframe bundling.

Various methods for transmitting a common control message such as an SIBmessage and a paging message to MTC UEs will be described below indetail.

3.1 Subframes for Repetition

Common control messages (e.g., SIB1 message) for MTC UEs may be designednewly, including all or part of information transmitted in legacy commoncontrol messages. For the convenience of description, one of the commoncontrol messages, SIB1 will be taken, and the same description isapplicable to other common control messages.

A SIB1 transmitted to general UEs is referred to as a legacy SIB1, and aSIB1 for MTC UEs is referred to as a MTC SIB1.

Transmission of legacy SIB1 starts in subframe (SF) #5 of a radio framesatisfying the relationship that SFN mod 8=0, and is repeated in SF #5satisfying SFN mod 2=0. Accordingly, legacy SIB1 is transmitted fourtimes during a time period of 80 ms.

For coverage improvement, common control messages may also be repeatedlytransmitted to MTC UEs. Repeated transmissions to an MTC UE means thatwith 4 repeated transmissions of legacy SIB1 during a time period of 80ms used as one set, this set is transmitted repeatedly a plurality oftimes.

Thus, if the legacy SIB1 transmission method for legacy UEs is stillused for MTC UEs, a latency will be increased in repeated transmissions.For example, if MTC SIB1 is transmitted repeatedly 100 times, 25 80-msperiod transmissions are required. That is, the time required forrepeated transmissions of MTC SIB1 is 2000 ms (=25*80 ms).

In this context, embodiments of the present disclosure propose novelmethods for transmitting MTC SIB1 to reduce a latency.

First of all, the eNB may also consider transmission of MTC SIB1 in anSF other than SF #5. Since it is preferable that reception of MTC SIB1at an MTC UE is not affected by PMCH transmission, the eNB transmits MTCSIB1 preferably in non-MBSFN SFs (e.g., SF #0, SF #4, and SF #9).

It is also preferable not to transmit unicast data for the MTC UE in anSF carrying MTC SIB1. Thus, as MTC SIB1 is transmitted in an entiremaximum bandwidth (e.g., 6 PRBs) supported for the MTC UE, the requirednumber of repeated transmissions of MTC SIB1 may be reduced.

That is, if an SF carrying MTC SIB1 is included in a time period duringwhich a PDSCH carrying MTC unicast data is repeatedly transmitted, theeNB does not transmit the PDSCH carrying the MTC unicast data. The MTCUE may also decode the SF, assuming that the repeated PDSCHs are nottransmitted in the SF carrying MTC SIB1.

3.2 Method for Transmitting PDCCH to Schedule Common Control Message

The eNB may transmit an MTC SIB1 message on a PDSCH in radio resources(i.e., 6 RBs) corresponding to a maximum bandwidth allowed for an MTCUE. If the eNB schedules the PDSCH delivering the MTC SIB1 message by aPDCCH/EPDCCH, control information of the PDCCH/EPDCCH does not need toinclude resource allocation information. This is because the MTC SIB1message is transmitted in the maximum bandwidth. Accordingly, thePDCCH/EPDCCH may include information about a Transport Block Size (TBS)and information about a repeated transmission number, instead ofresource allocation information.

The PDCCH/EPDCCH that schedules MTC SIB1 also needs to be repeatedlytransmitted because it is also transmitted to the MTC UE. However, ifthe last SF of the repeated transmissions is not SF #5 of a radio framesatisfying SFN mod 2=0, it is preferable to transmit the PDCCH/EPDCCH inSF #5 of the next earliest radio frame satisfying this relationship.Similarly, since MTC SIB1 starts to be transmitted in SF #5 of a radioframe satisfying SFN mod 8=0, if the last SF of the PDCCH/EPDCCHrepeated transmissions does not satisfy this relation equation, it ispreferable to transmit the PDCCH/EPDCCH in SF #5 of the next earliestradio frame satisfying this relation equation.

Since a processing time is required for decoding the repeatedlytransmitted PDCCH/EPDCCH, the PDSCH repeated transmissions may start ina k^(th) (k>1) SF after the last SF of the PDCCH/EPDCCH repeatedtransmissions, not in the last SF of the PDCCH/EPDCCH repeatedtransmissions. In this case, if the PDCCH/EPDCCH repeated transmissionsare not completed in SF #(5-k) of an RF satisfying SFN mod 8=0 or SFNmod 2=0, the eNB may start to transmit or repeatedly transmit the PDSCHfor transmission of MTC SIB1 in SF #5 of the next earliest radio framesatisfying the relation equation.

That is, although a PDCCH/EPDCCH including scheduling information forlegacy SIB transmission is transmitted in the same SF carrying an SIBmessage in the legacy system, the PDCCH/EPDCCH including schedulinginformation for MTC SIB1 transmission may be configured to betransmitted in a different SF from the SF carrying MTC SIB1.

If the repeated transmissions of MTC SIB1 take place in SFs other thanSF #5 of a radio frame satisfying SFN mod 2=0, the above method may beapplied in the same manner.

In another method, the starting time of the PDCCH/EPDCCH repeatedtransmissions may be fixed or indicated by a PBCH so that the PDSCHtransmission may occur in a corresponding radio frame to which the lastSF of the repeated transmissions of the PDCCH/EPDCCH scheduling thePDSCH for transmission of MTC SIB1 belongs.

If the system does not support the PDCCH/EPDCCH due to no need forscheduling the PDSCH for transmission of MTC SIB1, the number of PDSCHrepeated transmissions may be fixed or indicated by the PBCH. Or thenumber of PDSCH repeated transmissions may be determined based onanother parameter.

3.3 Method for Setting RVs

If an MTC SIB1 message is transmitted in SFs other than SF #5 due to itsrepeated transmissions, RVs may be set for a PDSCH carrying MTC SIB1 inthe SFs other than SF #5 in the following methods.

(1) Method 1

The RV of an SF in which MTC SIB1 starts to be transmitted may be set toRV0, and the RVs of subsequent SFs in which MTC SIB1 is repeatedlytransmitted may be set in the order of RV1, RV2, RV3, RV0, RV1 . . . orRV2, RV3, RV1, RV0, RV2 . . . . This method may bring the effect ofreducing repeated transmissions of an MTC SIB message by maximizing acoding gain.

(2) Method 2

The same RV may be set for a radio frame carrying MTC SIB1.

For example, if MTC SIB1 is transmitted in two SFs of a radio framecarrying MTC SIB1, the wireless access system may set an RV for SF #5 inthe same manner as for legacy SIB1, and the RVs of MTC SIB1 transmittedin the other SFs to the RV in SF #5.

That is, as an RV is changed on a frame-by-frame basis, the same RV maybe used for MTC SIBs repeatedly transmitted in the same radio frame. Dueto reuse of the legacy method, this method simplifies implementation ofthe reception functionality of an MTC UE, for MTC SIB1.

FIG. 12 is a view illustrating methods for repeatedly transmitting aPDCCH and setting RVs.

FIG. 12 illustrates the PDCCH repeated transmission and RV settingmethods described in sub-clauses 3.2 and 3.3 from the viewpoint ofsignaling. Referring to FIG. 12, the eNB may transmit a PDCCH/EPDCCHcarrying control information for MTC SIB transmission, repeatedly itimes. For a description of the PDCCH/EPDCCH, refer to sub-clauses 1.2and 1.7 (S1210).

The i-times repeated transmissions of the PDCCH/EPDCCH in step S1210 maybe performed according to the description of sub-clause 3.2. Forexample, while a PDCCH/EPDCCH for an MTC UE may be transmittedrepeatedly i times, if an MTC SIB is transmitted in a maximum systembandwidth allowed for the MTC UE, the PDCCH/EPDCCH may includeinformation about a TBS and/or the repetition number of the MTC SIB,instead of radio resource scheduling information. Further, SFs carryingthe PDCCH/EPDCCH may be configured to be different from SFs carrying therepeated MTC SIB.

The eNB may transmit an MTC SIBx message repeatedly j times based on thecontrol information transmitted on the PDCCH/EPDCCH (S1220).

When MTC SIBx is repeatedly transmitted j times in operation S1220, RVsmay be set for MTC SIBx according to the description of sub-clause 3.3.For example, if the repeated transmissions of the MTC SIBx message startin SF #a of radio frame #n, the RVs may be set in the order of {0, 1, 2,3, 0, . . . } or {0, 2, 3, 1, 0, . . . }, or the same RV (e.g., m) maybe set across radio frame #n.

3.4 CSI-RS Transmission Method

CSI-RSs are not transmitted in an SF carrying legacy SIB1 in order toavoid the performance degradation of legacy SIB1 caused by CSI-RStransmission in the LTE/LTE-A system.

In the case of MTC in coverage enhancement mode, an MTC SIB1 message maybe transmitted in an SF other than an SF carrying legacy SIB1. Herein,MTC SIB1 and CSI-RS transmissions may take place in an SF that does notcarry legacy SIB1. The eNB may transmit CSI-RSs in the followingmethods.

(1) Method 1

An MTC UE may assume that CSI-RSs are transmitted in none of SFscarrying MTC SIB1 like SFs carrying legacy SIB1. According to thismethod, although CSI feedback performance may be degraded due todiscontinuation of CSI-RS transmissions in proportion to repeatedtransmissions of MTC SIB1, the performance degradation of MTC SIB1 maybe avoided.

(2) Method 2

CSI-RSs may be transmitted as configured in SFs carrying MTC SIB1 exceptfor SFs carrying legacy SIB1. Although this method may avoid theperformance degradation of CSI feedback using CSI-RSs, it may degradethe performance of MTC SIB1. The performance degradation of MTC SIB1 maybe prevented by Method 2-1 or Method 2-2 as described below.

(3) Method 2-1

Regarding Method 2, the MTC UE may decode an MTC SIB1 message, assumingthat all REs available for CSI-RS transmission have been rate-matched.

(4) Method 2-2

Regarding Method 2, the MTC UE may decode a repeatedly transmitted MTCSIB1 message, assuming that CSI-RSs are not transmitted. In this case,the eNB may puncture REs for transmission of the MTC SIB message in acorresponding SF according to a CSI-RS configuration, map CSI-RSs to theREs, and transmit the CSI-RSs.

(5) Method 3

The eNB may transmit legacy CSI-RSs as configured, in SFs carryingrepeated MTC SIB1 other than SFs carrying legacy SIB1, except for a band(e.g., center 6 RBs) carrying MTC SIB1. Although this method bringsabout the performance degradation of CSI feedback for a band in whichCSI-RSs are not transmitted, it may not degrade the performance of MTCSIB1.

(6) Method 4

The eNB may be configured to transmit a specific CSI-RS configuration inSFs carrying MTC SIB1 except for SFs carrying legacy SIB1. In this case,the MTC UE may perform decoding, assuming that MTC SIB1 is rate-matchedin specific CSI-RS REs and transmitted in the remaining CSI-RS REs.

FIG. 13 is a view illustrating a CSI-RS transmission method, in the caseof repeated transmissions of an MTC SIB.

FIG. 13 is intended to describe a method for transmitting CSI-RSs asdescribed in sub-clause 3.4. Referring to FIG. 13, an eNB may transmitCSI-RS configuration information to a UE by a higher-layer signal. ForCSI-RSs and CSI-RS configuration information, sub-clause 1.6 may bereferred to (S1310).

If the eNB needs to transmit CSI-RSs according to the CSI-RSconfiguration information and transmit an MTC SIB to the MTC UE, the eNBmay transmit the MTC SIB and the CSI-RSs based on the description ofsub-clause 3.4.

For example, if the eNB should transmit the CSI-RSs and the MTC SIB inthe same SF (e.g., SF #n), the eNB may rate-match the CSI-RSs and theMTC SIB, or puncture the MTC SIB and map the CSI-RSs to correspondingREs, and transmit the CSI-RSs and the MTC SIB to the UE (S1320, S1330,and S1340).

If the MTC SIB is repeatedly transmitted j times in a plurality of SFs,the MTC SIB may be transmitted as it is in SFs not overlapped with theCSI-RSs.

3.5 Method for Configuring and Transmitting New SIB

In embodiments of the present disclosure, aside from MTC SIB1, systeminformation for MTC UEs may be newly defined. For the convenience ofdescription, the new system information will be referred to as MTC SIBx.MTC SIBx may define a time period (e.g., SI window) during which MTCSIBx may be transmitted, like a legacy SIB.

Preferably, MTC SIBx is transmitted in an SF that does not carry thePBCH and MTC SIB1, and preferably in non-MBSFN SFs (e.g., SF #0, SF #4,SF #5, and SF #9) to avoid collision with the PMCH. If repeatedtransmissions of MTC SIBx are not completed within the SI window, theymay continue in the next SI window.

A coverage enhancement-mode MTC UE may assume that a PDCCH/EPDCCH thatschedules a PDSCH carrying one MTC SIBx at maximum is repeatedlytransmitted within the SI window, in consideration of implementationcomplexity. It is preferred to complete repeated transmissions of thePDCCH/EPDCCH scheduling MTC SIBx within one SI window. Otherwise, it isassumed that MTC SIBx is not transmitted.

If MTC SIBx is transmitted, it is not preferable to transmit MTC SIBxand MTC unicast data at the same time. Therefore, like MTC SIB1, MTCSIBx may be transmitted in the maximum bandwidth (e.g., 6 PRBs) of anMTC UE, thereby reducing the number of repeated transmissions. RVs maybe set for MTC SIBx according to the foregoing RV setting method for MTCSIB1 as described in sub-clause 3.3.

3.6 Method for Transmitting Paging Message

A paging message is transmitted in an SF configured as a paging SF for acorresponding UE by a UE_ID and a related parameter configuration. Whenthe eNB configures paging messages, it is not preferred to transmitpaging messages for a legacy UE and an MTC UE on the same PDSCH.Therefore, a paging group is formed with MTC UEs.

A paging message may be transmitted in SFs (e.g., SF #4 and SF #9) thatdo not carry the PBCH or MTC SIB1/MTC SIBx.

In another method, if the sum of TBs for a paging message and MTCSIB1/MTC SIBx is equal to or less than a predetermined value, they maybe transmitted in the same SF.

To repeatedly transmit a paging message, one paging message may includea paging message for one MTC UE. Herein, the paging message may berepeatedly transmitted in paging SFs for the corresponding MTC UE. Inthe case where the repeated transmission period of the paging messageoverlaps with the transmission period of MTC SIB1/MTC SIBx, if the sumof TBs for the paging message and MTC SIB1/MTC SIBx is equal to or lessthan a predetermined value, they may be transmitted in an overlappedrepeated transmission period.

In another method, paging messages or the MTC SIB/MTC SIBx isprioritized, and only a paging message having a higher priority levelmay be transmitted. Resources used for an initially transmitted pagingmessage may be used for repeated transmissions of the paging message.

To reduce the number of repeated transmissions, the paging message maybe transmitted in a maximum bandwidth (e.g., 6 PRBs) supported by an MTCUE. RVs may also be set for the paging message in the same method asused for MTC SIB1 or MTC SIBx. If an SF carrying a paging messageoverlaps with an SF carrying CSI-RSs, the same method as used fortransmissions of MTC SIB1 and CSI-RSs may be applied to transmissions ofan MTC paging message and CSI-RSs.

3.7 Bandwidth Allocation Method

A legacy SIB, a paging message, and so on are scheduled by a PDCCHmasked with an SI-RNTI/P-RNTI in DCI format 1C. If transmission ofscheduling information in DCI format 1C is failed, the schedulinginformation may be transmitted in DCI format 1A by fallback. In thiscase, since DCI format 1A is larger in size than DCI format 1C, thecoding rate and the required SINR are increased. The resulting decreasein the number of PDCCH candidates may make it impossible for a UE at acell edge to receive a control signal. In this case, a PDSCH carrying alegacy SIB or a paging message may be transmitted in resources allocatedby a Distributed Virtual Resource Block (DVRB) resource allocationscheme.

MTC SIBs may be transmitted in up to center 6 RBs in a system bandwidth.With reference made to 3GPP TS 36.211/36.212/36.213, Virtual ResourceBlock (VRB) indexes affecting the center 6 RBs by DVRB allocation arelisted in [Table 12] to [Table 16].

TABLE 12 PRB index 9 10 11 12 13 14 15 VRB index in 13 17 21 2 6 10 14slot 0 VRB index in 15 19 23 0 4 8 12 slot 1

TABLE 13 PRB index 22 23 24 25 26 27 VRB index in 41 2 slot 0 VRB indexin 43 0 slot 1

TABLE 14 PRB index 22 23 24 25 26 27 VRB index in 32 34 19 23 27 20 slot0 VRB index in 33 35 21 25 29 18 slot 1

TABLE 15 PRB index 47 48 49 50 51 52 VRB index in 93 2 6 10 14 18 slot 0VRB index in 95 0 4 8 12 16 slot 1

TABLE 16 PRB index 47 48 49 50 51 52 VRB index in 61 34 38 42 46 50 slot0 VRB index in 63 32 36 40 44 48 slot 1

[Table 12] to [Table 16] list exemplary VRB indexes mapped to center 7RBs (if the bandwidth includes an odd number of RBs) or center 6 RBs (ifthe bandwidth includes an even number of RBs) according to DVRBallocation scheduled by DCI format 1C. [Table 12] to [Table 16] list VRBindexes for a 25-RB system bandwidth (about 5 MHz), VRB indexes for afirst group of values for a 50-RB system bandwidth (about 10 MHz), VRBindexes for a second group of values for the 50-RB system bandwidth, VRBindexes for a first group of values for a 100-RB system bandwidth (about20 MHz), and VRB indexes for a second group of values for the 100-RBsystem bandwidth, respectively.

As noted from [Table 12] to [Table 16], if the system bandwidth is lessthan 25 RBs, most of PRBs are mapped to center 6 RBs. For reference, inthe case of DVRB allocation scheduled by DCI format 1C, if the systembandwidth is less than 50 RBs, DVRBs are allocated in units of 2 RBs,and if the system bandwidth is equal to or greater than 50 RBs, DVRBsare allocated in units of 4 RBs. Accordingly, if an eNB and/or an MTC UErepeatedly transmits MTC data in subframes carrying a legacy SIB or apaging message, interference caused by the repeated transmissions maydegrade the performance of detecting the legacy SIB and/or the pagingmessage in legacy UEs.

Referring to [Table 12] to [Table 16], it is noted that the freedom withwhich the eNB performs scheduling, avoiding the center 6 RBs increasesrelatively in the 50-RB/100-RB system. Preferably, MTC user data/controldata is not scheduled in an SF carrying a legacy SIB or a pagingmessage.

Or depending on a system bandwidth, MTC user data/control data may beconfigured to be transmitted in an SF carrying a legacy SIB or a pagingmessage. For example, if the system bandwidth is less than x RBs, an MTCUE may perform decoding, assuming that MTC user data/control data is nottransmitted in an SF carrying a legacy SIB or a paging message. On theother hand, if the system bandwidth is equal to or greater than x RBs,the MTC UE may perform decoding, assuming that a legacy SIB or a pagingmessage is transmitted in an SF carrying MTC user data/control data.

Particularly, a legacy SIB1 message and an MTC SIB1 message may beconfigured to be transmitted in different SFs.

Or it may be configured that a legacy SIB1 message and an MTC SIB1message are transmitted in the same or different SFs depending onwhether the system bandwidth is less than y RBs, as described above(refer to clause 3.3).

3.8 MTC PDSCH Transmission Method

Aside from center 6 RBs of a system bandwidth, an MTC PDSCH may betransmitted repeatedly in other 6 RBs configured by the network. Thatis, 6 RBs at maximum may be configured as a system bandwidth for MTCUEs. For the convenience of description, the 6 RBs are referred to as anMTC subband.

The position of the MTC subband may be changed over time. The positionof the MTC subband may be changed in the frequency domain over time, forexample, MTC subband x occupies PRB #0 to PRB #5 at time n (or insubframe #n), and PRB #6 to PRB #11 at time n+k (k>0).

Or a higher layer may configure a plurality of MTC subbands, and the eNBmay be configured to transmit the MTC PDSCH in a different MTC subbandwith passage of time.

Meanwhile, compared to a legacy PBCH which is transmitted in SF #0 every40 ms, MTC PBCH repeated transmissions may be configured to take placeduring a specific time period. Herein, an MTC subband carrying the MTCPDSCH and a band in which the MTC PBCH is repeatedly transmitted mayoverlap with a part or all of the center 6 RBs. In this case,considering that the repeated transmissions of the MTC PBCH consume muchtime and frequency resources, resources may be used efficiently byallowing the higher layer to enable or disable the repeatedtransmissions of the MTC PBCH in a specific time period.

Due to no knowledge of on/off of the MTC PBCH repeated transmissions,the MTC UE preferably performs decoding, assuming that the MTC PDSCH isnot transmitted in a PRB of the MTC subband, overlapped with the center6 RBs. That is, the MTC UE assumes that the MTC PDSCH is not transmittedat all in an MTC PBCH repeated transmission period in which the MTC PBCHis likely to be transmitted, irrespective of on/off of the MTC PBCHrepeated transmissions.

For example, if the MTC PBCH is transmitted in SF #0 and/or SF #5, theMTC UE may perform decoding, assuming that the MTC PDSCH is nottransmitted in a part or all of RBs overlapped with the center 6 RBs inSF #0 and/or SF #5.

3.9 Method for Transmitting Control Signal in NB-IoT System

UE cost may further be reduced by supporting a bandwidth of only 1 PRBfewer than 6 PRBs for a system supporting MTC. This system may bedefined as an NB-IoT system. Further, a UE supporting operations of theNB-IoT system may be referred to as an NB-IoT UE. The following threeoperation modes are defined for the NB-IoT system.

(1) In-band operation mode: In the in-band operation mode, a specificPRB of the legacy LTE/LTE-A system is allocated to NB-IoT.Advantageously, the already deployed LTE/LTE-A system may be utilized.

(2) Guard band operation mode: In the guard band operation mode, anNB-IoT band is allocated in a guard band configured to preventinterference between adjacent bands in the LTE/LTE-A system.

(3) Stand-alone operation mode: In the stand-alone operation mode, afrequency band corresponding to 1 PRB is allocated only for NB-IoT,irrespective of an LTE/LTE-A system band. For example, a frequency bandused for legacy GSM (e.g., one channel is 200 KHz) may be allocated forthe NB-IoT system. This operation mode is advantageous in that there arenone of limitations on resource utilization, caused by transmission of acommon control channel or signal from the legacy LTE/LTE-A system.

In the in-band operation mode, a specific PRB used in the legacyLTE/LTE-A system is allocated for the NB-IoT system. Therefore, it ispreferred to allocate the PRB for supporting NB-IoT in alignment withthe boundary of a PRB used in the LTE/LTE-A system. Otherwise, eventhough one PRB is allocated as an NB-IoT band, resources across two PRBsdefined in the LTE/LTE-A system should be used, thereby decreasing theresource use efficiency of the LTE/LTE-A system.

The center frequency of the LTE/LTE-A system is set to a multiple of 100KHz. As a consequence, a UE may perform cell search, while shifting thecenter frequency in units of 100 KHz, which reduces the implementationcomplexity of the UE. Accordingly, it is also preferred to set thecenter frequency to a multiple of 100 KHz for an NB-IoT UE.

In the in-band operation mode, therefore, it may be configured that thecenter frequency of the NB-IoT system is set to a multiple of 100 KHzand a PRB aligned with the boundary of a PRB used in the legacyLTE/LTE-A system is used in the NB-IoT system. In this case, the NB-IoTcenter frequency may not be the center frequency of the correspondingPRB, but may be at a frequency position with a misalignment of at least2.5 KHz or 7.5 KHz depending on the LTE/LTE-A system bandwidth. Thus,the same effect as causing an additional frequency offset of 2.5 KHz or7.5 KHz may occur to the NB-IoT UE.

FIG. 14 is a view illustrating a relationship between the centerfrequency of NB-IoT and the center frequency of an LTE/LTE-A system inthe in-band operation mode.

Referring to FIG. 14, when the center frequency is set to a multiple of100 KHz in the NB-IoT system, a generated center frequency of the NB-IoTsystem may be checked. In FIGS. 14(a) and 14(b), let each bandwidth bedefined as a raster. Then, the center frequency of a raster in theLTE/LTE-A system and the center frequency of an NB-IoT PRB are placed inthe relationship illustrated in FIG. 14. In FIG. 14, f_(LTE) representsthe center frequency of the LTE/LTE-A system, and f_(NB-IoT) representsthe center frequency of the NB-IoT system.

FIG. 14(a) illustrates a case in which a system bandwidth is configuredto include an odd number of PRBs (e.g., 3 MHz, 5 MHz, 15 MHz, or thelike), and FIG. 14(b) illustrates a case in which a system bandwidth isconfigured to include an even number of PRBs (e.g., 10 MHz, 20 MHz, orthe like).

The center frequency of an NB-IoT band on the right side of each ofFIGS. 14(a) and 14(b) will be taken as an example, for description. Ifthe system bandwidth of the LTE/LTE-A system has an odd number of PRBs,the center frequency exists in the middle of a PRB. Therefore, thecenter frequency is set to 100 n+180 m+7.5 KHz (m=4, 5, 6, . . . ). Ifthe system bandwidth of the LTE/LTE-A system has an even number of PRBs,the center frequency may be represented as 100 n+180 m+97.5 KHz (m=3, 4,5, . . . ). In this manner, the center frequency of an NB-IoT band onthe left side of each of FIGS. 14(a) and 14(b) may be configured.

Herein, because the center 6 RBs are used to transmit a control signalfor legacy UEs and may be allocated for MTC UEs, the center 6 RBs maynot be allocated to an NB-IoT UE. Therefore, it may be configured thatm=4, 5, . . . in a system bandwidth having an odd number of PRBs, andm=3, 4, 5, . . . in a system bandwidth having an even number of PRBs.

If values of m are substituted in the center frequency of a bandwidthincluding an odd number of PRBs, f_(NB-IoT) is set to 187.5, 367.5,547.5, 727 . . . 5, 907.5 KHz. Thus, the difference between 907.5 KHzand a multiple of 100 KHz, 900 KHz is 7.5 KHz. In addition, if values ofm are substituted in the center frequency of a bandwidth including aneven number of PRBs, PRB indexes having a frequency difference of 2.5KHz may be obtained.

Center frequency offsets which may be generated according to LTE/LTE-Asystem bandwidths in the case of alignment with a PRB boundary of theLTE/LTE-A system in the in-band operation mode will be described below.

(A) If the system bandwidth is 10 or 20 MHz: the offset between thecenter frequency and the PRB center frequency may be 2.5 KHz, 17.5 KHz,22.5 KHz, 37.5 KHz, or 42.5 KHz.

(B) If the system bandwidth is 3.5 or 15 MHz: the offset between thecenter frequency and the PRB center frequency may be 7.5 KHz, 12.5 KHz,27.5 KHz, 32.5 KHz, or 47.5 KHz.

In the cases of (A) and (B), therefore, a PRB of the LTE/LTE-A systemcorresponding to a minimum offset between the center frequencies, whichis 2.5 or 7.5 KHz is preferably allocated as a PRB for the NB-IoTsystem. [Table 17] below lists PRB indexes and VRB indexes with anoffset of 2.5 or 7.5 KHz according to LTE/LTE-A system bandwidths.

TABLE 17 LTE/LTE-A system bandwidth 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz PRBindex — — 4, 9, 14, 19, — 4, 9, 14, 19, 24, 29, with offset of 30, 35,40, 45 34, 39, 44, 55, 60, 2.5 KHz 65, 70, 75, 80, 85, 90, 95 VRB index— — Gap1: (16, 18), Gap1: with offset of (36, 38), (9, 11), (16, 18),(36, 38), 2.5 KHz (29, 31), (14, (9, 11), (29, 31), (1, 12), (34, 32),3), (21, 23), (41, (5, 7), (25, 27), 43), (61, 63), (81, Gap2: (14, 15),83), (6, 4), (30, 28), (0, 2) (17, 16), (50, 48), (70, 68), (22, 24),(31, (90, 88), (15, 13), 30), (29, 27) (35, 33), (55, 53), (75, 73),(95, 93) Gap2: (14, 15), (0, 2) (17, 16), (22, 24), (3, 1), (21, 23),(40, 42), (60, 62), (49, 51), (38, 36), (62, 60), (51, 49), (68, 70),(88, 90), (77, 79), (66, 64), (86, 84), (95, 93), (75, 73) PRB index 2,12 2, 7, — 2, 7, 12, 17, — with offset of 17, 22 22, 27, 32, 7.5 KHz 42,47, 52, 57, 62, 67, 72 VRB index (8, 10), (8, 10), — Gap1: (8, — withoffset of (3, 1) (5, 7), 10), (28, 30), 7.5 KHz (20, 22), (48, 50), (5,(19, 17) 7), (25, 27), (45, 47), (0, 2), (42, 40), (62, 61), (19, 17),(59, 57) Gap2: (8, 10), (28, 30), (17, 19), (6, 4), (26, 24), (13, 15),(32, 34), (41, 43), (60, 63), (50, 48), (59, 57)

[Table 17] lists VRB indexes mapped to PRB indexes that may be borrowedfrom the LTE/LTE-A system, as a system bandwidth supporting the NB-IoTsystem in the in-band operation mode. Herein, numbers in a bracketrepresent two VRB indexes mapped to one PRB index. In addition, VRBindexes are listed in the order of PRB indexes in [Table 17].

For example, PRB indexes having an offset of 7.5 KHz among the PRBindexes of an LTE-A system having a 3-MHz band may be 2 and 12. Herein,VRB indexes mapped to PRB indexes 2 and 12 are respectively (8, 10) and(3, 1). In this manner, the position of a bandwidth to be allocated toan NB-IoT UE may be determined based on the mapping relationship betweenPRB indexes and VRB indexes, illustrated in [Table 17].

In this case, if a common control message of the legacy LTE/LTE-A systemis transmitted in a DVRB, the eNB preferably selects a PRB unused forDVRB transmission among the PRB indexes of [Table 17], referring to[Table 12] to [Table 16] and allocates the selected PRB as an NB-IoTband. For example, in an LTE/LTE-A system having a bandwidth of 15 MHz,PRB indexes 64 to 74 are not used for DVRB transmission, and thus asystem entity such as an eNB preferably allocates PRB index 72 of theLTE/LTE-A system as a system band for NB-IoT.

In another method, if the NB-IoT operates in the in-band operation mode,an NB-IoT UE performs decoding, assuming that DVRB transmission does nottake place in the PRBs listed in [Table 17]. That is, when the PRBindexes listed in [Table 17] are allocated to NB-IoT, the eNB mayperform resource allocation such that the PRBs may not be scheduled forDVRBs.

If DVRB transmission takes place in a PRB, the eNB may drop the DVRBtransmission in the PRB to be transmitted to an NB-IoT UE and scheduleDVRB transmission in the remaining PRBs.

Or if DVRB transmission takes place in the PRB, the eNB may minimize theeffect of the DVRB transmission on the legacy system by puncturing datato be transmitted to the NB-IoT UE.

FIG. 15 is a view illustrating a method for allocating a bandwidth fortransmitting a common control signal or data to an NB-IoT UE.

Referring to FIG. 15, the eNB may transmit, to an NB-IoT UE and/or alegacy UE, control information including resource allocation information(e.g., a PRB index and/or a VRB index) indicating resources available asa bandwidth for the NB-IoT system by a PDCCH, EPDCCH, MAC signal, or RRCsignal (S1510).

However, step S1510 may be configured to be optional according to systemrequirements.

The eNB may allocate resources in which a common control signal or datawill be transmitted, based on a PRB index supportable as an NB-IoT band.Herein, the eNB may allocate a VRB mapped to the PRB index as describedwith reference to [Table 17], for the NB-IoT band, avoiding VRBscorresponding to DVRBs as described before with reference to [Table 12]to [Table 16] (S1520).

That is, the eNB preferably avoids VRBs that may affect the center 6 RBsof the bandwidth in step S1520. In addition, in the case of alignmentwith a PRB boundary of a legacy system (e.g., the LTE/LTE-A system), aVRB mapped to a PRB that minimizes the offset between the centerfrequency of the NB-IoT system and the PRB center frequency of thelegacy system may be allocated as the NB-IoT band.

The eNB may transmit a PDSCH carrying the common control signal and/orthe data in the allocated NB-IoT band (S1530).

In step S1530, the common control signal and/or the data may betransmitted repeatedly. Since NB-IoT may be regarded as a kind of MTC, acommon control signal and/or data for an NB-IoT UE may be transmittedand received repeatedly, like a common control signal and/or data for anMTC UE. For the technical features of the method of repeatedtransmissions/receptions for an NB-IoT UE, the embodiments described inclause 2 to clause 3.8 may be applied.

If step S1510 is not performed in FIG. 15, the NB-IoT UE may search fora bandwidth allocated to it based on predetermined resource allocationinformation (i.e., VRB index information) as listed in [Table 17].Further, the NB-IoT UE may receive common control information or data inthe detected bandwidth.

4. Apparatuses

Apparatuses illustrated in FIG. 16 are means that can implement themethods described before with reference to FIGS. 1 to 15.

A UE may act as a transmission end on a UL and as a reception end on aDL. An eNB may act as a reception end on a UL and as a transmission endon a DL.

That is, each of the UE and the eNB may include a Transmitter (Tx) 1640or 1650 and a Receiver (Rx) 1660 or 1670, for controlling transmissionand reception of information, data, and/or messages, and an antenna 1600or 1610 for transmitting and receiving information, data, and/ormessages.

Each of the UE and the eNB may further include a processor 1620 or 1630for implementing the afore-described embodiments of the presentdisclosure and a memory 1680 or 1690 for temporarily or permanentlystoring operations of the processor 1620 or 1630.

The embodiments of the present disclosure may be implemented using thecomponents and functions of the above-described UE and eNB. For example,the processor of the eNB may configure a resource area to be allocatedto an NB-IoT system. Herein, with a VRB corresponding to a DVRB that mayaffect center 6 RBs avoided, a PRB that minimizes the difference (i.e.,frequency offset) between a center frequency and a PRB center frequencyaccording to the bandwidth of a legacy system may be allocated as anNB-IoT band. The processor of the eNB may transmit common controlinformation or data to an NB-IoT UE in a VRB mapped to the PRB allocatedas the NB-IoT band. For details, refer to clause 1 to clause 3.

The Tx and Rx of the UE and the eNB may perform a packetmodulation/demodulation function for data transmission, a high-speedpacket channel coding function, OFDM packet scheduling, TDD packetscheduling, and/or channelization. Each of the UE and the eNB of FIG. 16may further include a low-power Radio Frequency (RF)/IntermediateFrequency (IF) module.

Meanwhile, the UE may be any of a Personal Digital Assistant (PDA), acellular phone, a Personal Communication Service (PCS) phone, a GlobalSystem for Mobile (GSM) phone, a Wideband Code Division Multiple Access(WCDMA) phone, a Mobile Broadband System (MBS) phone, a hand-held PC, alaptop PC, a smart phone, a Multi Mode-Multi Band (MM-MB) terminal, etc.

The smart phone is a terminal taking the advantages of both a mobilephone and a PDA. It incorporates the functions of a PDA, that is,scheduling and data communications such as fax transmission andreception and Internet connection into a mobile phone. The MB-MMterminal refers to a terminal which has a multi-modem chip built thereinand which can operate in any of a mobile Internet system and othermobile communication systems (e.g. CDMA 2000, WCDMA, etc.).

Embodiments of the present disclosure may be achieved by various means,for example, hardware, firmware, software, or a combination thereof.

In a hardware configuration, the methods according to exemplaryembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the methods according to theembodiments of the present disclosure may be implemented in the form ofa module, a procedure, a function, etc. performing the above-describedfunctions or operations. A software code may be stored in the memory1680 or 1690 and executed by the processor 1620 or 1630. The memory islocated at the interior or exterior of the processor and may transmitand receive data to and from the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentdisclosure or included as a new claim by a subsequent amendment afterthe application is filed.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to various wireless access systemsincluding a 3GPP system, a 3GPP2 system, and/or an IEEE 802.xx system.Besides these wireless access systems, the embodiments of the presentdisclosure are applicable to all technical fields in which the wirelessaccess systems find their applications.

1. A method for transmitting a common control message in a wirelessaccess system supporting Narrow Band Internet of Things (NB-IoT), themethod comprising: allocating a bandwidth for the NB-IoT; andtransmitting a common control message in the allocated bandwidth,wherein the bandwidth is configured to be aligned with a boundary of aPhysical Resource Block (PRB) used in a legacy system, wherein a PRBwhich minimizes an offset between a center frequency of the bandwidthand a center frequency of the PRB is allocated as the bandwidth for theNB-IoT, in consideration of a bandwidth of the legacy system, andwherein the PRB allocated as the bandwidth for the NB-IoT is not used asa Distributed Virtual Resource Block (DVRB) in the legacy system.
 2. Themethod according to claim 1, wherein Virtual Resource Blocks (VRBs)which are mapped to the PRB allocated as the bandwidth for the NB-IoTare used for the transmission of the common control message.
 3. Themethod according to claim 1, wherein the bandwidth is allocated otherthan a VRB affecting center 6 RBs of the legacy system.
 4. The methodaccording to claim 1, wherein the common control message is transmittedrepeatedly a predetermined number of times.
 5. An apparatus fortransmitting a common control message in a wireless access systemsupporting Narrow Band Internet of Things (NB-IoT), the methodcomprising: a transmitter; and a processor for supporting transmissionof a common control message, wherein the processor allocates a bandwidthfor the NB-IoT, and transmits the common control message in theallocated bandwidth by controlling the transmitter, wherein thebandwidth is configured to be aligned with a boundary of a PhysicalResource Block (PRB) used in a legacy system, wherein a PRB whichminimizes an offset between a center frequency of the bandwidth and acenter frequency of the PRB is allocated as the bandwidth for theNB-IoT, in consideration of a bandwidth of the legacy system, andwherein the PRB allocated as the bandwidth for the NB-IoT is not used asa Distributed Virtual Resource Block (DVRB) in the legacy system.
 6. Theapparatus according to claim 5, wherein Virtual Resource Blocks (VRBs)which are mapped to the PRB allocated as the bandwidth for the NB-IoTare used for the transmission of the common control message.
 7. Theapparatus according to claim 5, wherein the bandwidth is allocated otherthan a VRB affecting center 6 RBs of the legacy system.
 8. The apparatusaccording to claim 5, wherein the common control message is transmittedrepeatedly a predetermined number of times.